Check a dictionary, and you'll see pizza defined as a "baked open-faced pie consisting of a thin layer of dough topped with tomato sauce and cheese." But chefs worldwide stretch not only the dough, but the definition as well. On my first trip to Italy in 1976 I discovered tomato-less pizza. The delicious pizza bianca (white pizza) was crowned only with herbs and cheese. According to Il Libro D'oro Dei Primi Piatti Italiani ("The Golden Book of Italian First Courses") by Fiamma Niccolini Adimari & Fosco Provvedi (Mursia, Milano, 1980), you make it by topping the dough with mozzarella slices, basil leaves and salt. Evelyne Slomon, author of The Pizza Book (Times, 1984) bakes several kinds of white pizza Roman style with onions, rosemary and mozzarella, Genoan with pesto and two kinds of cheese and Palmero with mozzarella, herbs, anchovies and black olives. Pizza doesn't necessarily have cheese, either. At cooking school in Paris, our chefs made elegant seafood pizza, sans cheese. Pizza with soy cheese is the choice of vegans and cooks who want parve pizza. Cheeseless pizza topped with roasted vegetables like onions, peppers and eggplant can be wonderful. My friend Evan Kleiman, the chef-owner of Angeli Caffe in Los Angeles, has a simple pizza aglio e olio on her menu - garlic and olive oil solo, as in the classic spaghetti dish. These examples prove that pizza can be healthy. Use whole wheat flour in the crust, add a vegetable or herb topping with a little soy or dairy cheese and a drizzle of extra virgin olive oil, and even nutrition-conscious eaters can enjoy "guilt-free" pizza. The pizza base isn't always the usual bread dough. Kleiman and co-author Viana La Place, in their book Cucina Rustica (Morrow, 1990), bake Puglian potato pizza with a mashed potato crust and a smoked mozzarella-tomato topping. Recently I sampled Amy's Rice-Crust Pizza at the Natural Products Expo in Anaheim, California. Created from rice flour for people allergic to wheat, it tasted fine to me. Pizzas baked on bagels are a popular frozen product in the US; I think of them as a variation of pita pizzas, the Israeli mothers' improvisation for a quick supper for their kids. For carbophobes there is even pizza with an eggplant base instead of dough. Today's pizza bakers see the world's cuisines as their flavor palette. I've had curry pizza, and to my surprise, it was good! When Austrian-born California chef Wolfgang Puck created smoked salmon pizza with dill creme fraiche, this pizza take on the bagel-lox-cream cheese theme created a sensation. Authors Larry Flax & Rick Rosenfield of The California Pizza Kitchen Cookbook (Macmillan, 1996) make barbecue chicken pizza with spicy-sweet barbecue sauce, and Thai chicken pizza with spicy peanut sauce. So what's a pizza? Tomatoes and cheese aren't necessary, and there is no standard crust. Of the dictionary definition, we're left with "a baked open-face pie." But even that's not necessarily true anymore - now there's raw pizza! The "rawists" make crusts of nuts, seeds, vegetables and sprouted grains, dried in a dehydrator instead of being baked. At the Expo I tasted Rawsheed's raw vegan "Sicilian Pizza," with a base of ground almonds flavored with oregano and garlic, and a topping of sun dried tomato sauce and cashew nut "cheese." With such good ingredients, I guess I shouldn't have been surprised at how yummy it was. PARVE MUSHROOM-PISTOU PIZZA This pizza is flavored with French pistou, a cousin of Italian pesto that's often cheese-free. Dough: 11â„2 cups whole wheat flour 11â„2 cups all purpose flour 7 gr. dry yeast or 15 gr. fresh, crumbled 1 cup plus 2 Tbsp. lukewarm water 2 Tbsp. extra virgin olive oil 11â„2 tsp. salt Topping: 1 or 2 garlic cloves, peeled 1â„3 cup fresh basil leaves about 5 Tbsp. extra virgin olive oil 2 tomatoes, fresh or canned salt and freshly ground black pepper 2 medium onions, halved, sliced thin 1 sweet red pepper, cut in thin strips 110 to 170 gr. mushrooms, halved and sliced thin To make dough in mixer with dough hook: Sift both kinds of flour into mixer bowl and make a well in center. Sprinkle yeast into well. Pour 1â„3 cup water over yeast and let stand for 10 minutes. Stir until smooth. With mixer on low speed, gradually add remaining water, oil and salt to well. Stir flour into well and mix for 2 minutes to blend. Mix at medium speed, adding flour if dough is too wet or water if it's too dry, until dough clings to hook and cleans side of bowl (you can also make dough by hand or in a large food processor). Lightly oil a medium bowl. Add dough, turning to coat entire surface. Cover with a damp towel and let rise in a warm place about 30 minutes or until doubled in volume. For topping, make pistou: grind garlic, basil and 1 tablespoon oil in a small food processor. If using fresh tomatoes, peel if desired, dice and sprinkle with salt. Drain fresh or canned tomatoes in a colander about 5 minutes. Heat 2 tablespoons oil in a large skillet. Add onions and cook over medium-low heat for 10 minutes or until softened. Add pepper strips, salt and pepper and cook, stirring often, for 7 minutes or until just tender. Transfer mixture to a bowl and stir in pistou. Taste and adjust seasoning. Heat another tablespoon oil in skillet. Add mushrooms, salt and pepper. Saute for 3 minutes or until mushrooms brown lightly. Oil 2 baking sheets. Knead dough briefly, divide in two and put each part on a baking sheet. With oiled hands, pat each in a 25-cm. round, making rims slightly higher than centers. Preheat oven to 200 c. Spread half of onion mixture over each pizza, leaving 1â„2-inch edges. Top with mushrooms and tomato. Brush dough's edges with oil and drizzle a little oil over topping. Bake for 16 to 18 minutes or until dough is golden brown and firm but not hard. Serve hot or warm. Makes 6 to 8 servings. Faye Levy is the author of Feast from the Mideast (HarperCollins) and 1,000 Jewish Recipes (Wiley).