Melt 3 tablespoons butter in a medium skillet over medium-high heat. Saute onion until golden.
In a 2 quart casserole dish, mix together onion, broccoli, soup, cheese, mayonnaise, eggs, garlic salt, pepper, seasoned salt, and lemon juice. Sprinkle crushed crackers over top and dot with remaining 2 tablespoons butter.
Bake uncovered in preheated oven for 45 minutes, until heated through and browned on top.