Preheat oven to 375 degrees and spray a large casserole dish with nonstick spray.
Slice the squash into 1/4" slices. If they are larger squash, cut them down the middle before slicing.
Heat oil in a large non-stick frying pan.
Add the squash, garlic, and thyme.
Sauté and stir until the squash is just starting to soften. Don't overcook!
Remove from heat and add tomatoes.
Beat together the eggs, sour cream, cheeses, and lemon juice in a medium sized bowl.
Place half of the squash into the bottom of the casserole (you can be fancy and layer it like in the picture or you can just toss it in).
Sprinkle on some salt and pepper then spread 1/2 of the egg mixture over the top.
Repeat with remaining squash and egg mixture.
Top with additional feta and Parmesan if desired.
Bake for 40-45 minutes, until the mixture is bubbling and slightly set.