Remove and discard leaves and stem from cauliflower.
Cut around core with paring knife, being careful not to separate flowerets from head; remove and discard core.
Rinse.
Pour 1 inch of water into large saucepan.
Place cauliflower in water, stem side down; cover.
Bring to a boil over high heat; reduce heat to low.
Simmer 10 to 12 minutes or until crisp-tender; drain.
Place cauliflower in 8-inch square baking dish.
Preheat oven to 375°F.
Melt butter over medium heat in small skillet.
Stir in bread crumbs and onions; cook until crumbs are lightly browned.
Stir in eggs and lemon juice.
Press crumb mixture evenly over top of cauliflower.
Place any extra crumb mixture in baking dish.
Bake 10 minutes or until crumb mixture is crispy and lightly browned.
Garnish, if desired.