Heat olive oil in a small pan and saute onions and garlic until onions become translucent, being careful not to burn garlic. Stir in tomato paste and 2 cups water and season with salt and pepper, to taste. Cover and cook over low heat for approximately 15 minutes, or long enough to allow flavors to integrate into a sauce.
Preheat oven to 350 degrees F. Lay 1/4 (about 15) of the wontons over the bottom of a lasagna dish, followed by a layer each of yellow squash, zucchini, eggplant, fresh tomato, about 1/2 cup tomato sauce, and 1/2 cup of the ricotta. Repeat for a total of 4 layers, finishing on the top layer with the mozzarella. Bake for about 30 minutes covered with foil, and about 10 minutes more uncovered. Remove from oven and let rest 10 minutes. While the lasagna is in the oven, begin the red pepper coulis.
For the Coulis:
Whisk the cornstarch into the chicken broth. Melt the butter over medium heat in a saute pan, and then add the chicken broth mixture, red peppers and garlic. Simmer 30 minutes. Pour hot mixture into blender and blend until smooth to make red pepper sauce.
Spoon some red pepper coulis onto serving plate and place a square of lasagna on top. Garnish with fresh basil sprigs.