Remove and discard stems and center ribs of collard greens. Cut leaves into 1-inch pieces. In a kettle of boiling water cook collards 15 minutes and drain in a colander, pressing out excess liquid with back of a wooden spoon.

Mince garlic. In a 12-inch heavy skillet heat butter and oil over moderately high heat until foam subsides and stir in garlic, collards, and salt and pepper to taste. Sauté collard mixture, stirring, until heated through, about 5 minutes.

Drizzle collards with lemon juice and toss well.