For the filling
01 -
2.5 lb (1.1 kg) yellow summer squash, sliced 1/4 inch thick
02 -
1 medium sweet onion, chopped
03 -
2 tablespoons unsalted butter
04 -
1/2 cup sour cream
05 -
1/3 cup mayonnaise
06 -
2 large eggs
07 -
1 1/2 cups shredded sharp cheddar cheese, divided
08 -
1/2 cup grated Parmesan cheese
09 -
1/2 teaspoon garlic powder
10 -
1 teaspoon kosher salt
11 -
1/2 teaspoon black pepper
For the topping
12 -
1 sleeve buttery crackers (about 30 Ritz), crushed
13 -
3 tablespoons unsalted butter, melted