Squash and Onions Recipe 2 tablespoons butter or olive oil 5 medium yellow squash, sliced ½ medium sweet onion, diced salt and pepper to taste Melt butter over medium-low heat in a skillet. Add squash and onions and cook until onions are translucent and squash has become fork tender, about 8-10 minutes. Remove from heat. Add salt and pepper to taste. Serve warm.