Preheat the oven to 350F degrees. Butter a baking dish. Sprinkle the 2 tbsp of cornmeal into the baking dish making sure the bottom and sides are coated. Shake out the excess.
Heat a large deep skillet over medium heat with the olive oil. Add the onions and garlic and allow them to cook until the onions are translucent.
Add the corn and zucchini and season with salt, pepper, and red pepper flakes if using. Let them cook until soft and tender, 5-10 minutes.
Remove from the heat and set aside.
Add the eggs, yogurt, cornmeal, and heavy cream to a bowl and whisk together.
Stir in the fresh herbs and feta. Check for seasoning.
Spread the zucchini and corn mixture into the bottom of the prepared baking dish. Pour the egg and cheese mixture over the top.
Allow the quiche to bake for 40-45 minutes until golden brown, puffed, and the eggs are set.