In a large skillet, melt butter and olive oil. Add sliced onions and stir to coat the onions in the butter and oil.
Wrap approximately 10-15 thyme sprigs with butcher’s twine and add the thyme bundle, salt, and pepper to the onions.
Cook and stir the onions occasionally until they've cooked down, become translucent and turned a deep golden brown.
Set the onions aside. *Note - the onions can be made up to 3 days in advance and stored (covered) in the refrigerator if needed.
Meanwhile, while the onions are cooking, slice the tomatoes and zucchini into ¼" rounds. Place the vegetables on a rack or paper towel and season them with salt and pepper. Set the vegetables aside.
In a large bowl, stir together the cornmeal, cornflake crumbs, salt, pepper, Parmesan cheese, sugar, melted butter, and egg.
Once the mixture resembles coarse crumbs, press the crust mixture into a 9" tart pan which has been sprayed liberally with cooking spray.
Place the prepared pan on a baking sheet, and press the crumbs evenly up the sides, and the bottom of the tart pan.
• Bake in a preheated 400-degree oven for 10-12 minutes. Remove the crust from the oven.
Gently blot the vegetables from any excess moisture that has formed on top.
In a small bowl, stir together the mayonnaise and minced garlic.
Spread the mayonnaise mixture evenly on over the base of the pre-baked tart crust.
Top the mayonnaise layer evenly with the thyme-infused caramelized onions (thyme bundle removed and discarded).
Layer the dried tomato and zucchini slices in a decorative pattern over the caramelized onions.
Sprinkle Parmesan cheese over the vegetables and bake in a preheated 400-degree oven for 20 minutes.
Remove the tart from the oven an cool on a rack for 15 minutes.
Allow the sides of the tart pan to fall away by using a small bowl to prop up the center of the tart.
To serve, place the tart on a decorative plate and garnish with additional thyme sprigs if desired.
Tools and equipment;
9" tart pan with removable bottom, baking spray, large skillet, wooden spoon or spatula, measuring cups, measuring spoons, chef's knife, cutting board, paper towels, large bowl, butcher's twine