For the crust: Preheat the oven to 350 degrees F for 5 minutes. Turn the oven off.
In a large bowl, whisk together 1 cup warm water (105 to 115 degrees F), yeast and salt; let stand for 5 minutes. Stir in the flour, sugar, Italian seasoning and oil. Loosely cover, and let rise in a warm oven until the dough is doubled in size, about 1 hour. Remove the dough from the oven.
Sprinkle some cornmeal on a 14-inch pizza pan. Turn the dough out onto a lightly floured surface and knead 6 to 8 times. Pat the dough onto the prepared pizza pan to make a 14-inch pizza crust. Let rise in a warm place (about 85 degrees), free from drafts, for 20 minutes.
Meanwhile, preheat the oven to 450 degrees F.
Bake the pizza crust until no longer wet, about 8 minutes. Remove from the oven, and let cool for 10 minutes.
For the topping: In a large saucepan, heat the oil over medium heat. Add the onions, squash and zucchini and saute until lightly browned, about 10 minutes.
Combine the cream cheese, ranch dressing, sour cream and a pinch of salt and pepper. Spread the cheese mixture evenly over the pizza crust, leaving a 1-inch border. Arrange the vegetables and the tomatoes over the cheese, then top with basil leaves. Sprinkle with 1/4 teaspoon salt, 1/4 teaspoon pepper and garlic. Top with the mozzarella and Parmesan and bake directly on the oven rack until golden, about 8 minutes. Remove from the oven, and transfer to a cutting board. Cut into wedges.
Cook's Note: You can use store bought pizza dough for this recipe.