Preheat oven to 350°F.
Heat 1 teaspoon oil in a small skillet over medium heat. Add ¼ cup onion; cook until translucent and beginning to soften, about 2 minutes.
Combine drained spinach, the onion, 1 cup cottage cheese, ½ cup each feta and Monterey Jack, 2 beaten eggs, 1 teaspoon each garlic powder and lemon juice and ⅛ teaspoon salt in a 2-quart casserole dish. Top with 2 tablespoons Parmesan. Bake until the casserole is bubbling and the top is beginning to brown, 40 to 45 minutes. Let stand for 10 minutes.
