1 1/2 lbs. yellow summer squash
1/4 c. onion, chopped
1/4 c. cracker meal or bread crumbs
1 egg
1/4 c. butter, divided & melted
1 1/2 tsp. sugar
1/2 tsp. salt (or to taste)
1/4 tsp. black pepper (or to taste)
Crumbs (to sprinkle over casserole)