Prepare rice according to package directions.
Melt butter in a large skillet over medium-high heat; add ham, onion, and garlic, and sauté 6 to 7 minutes or until onion is tender. Stir in black-eyed peas and 1/2 cup water. Bring to a boil; reduce heat, and simmer 10 minutes. Stir in vinegar.
Place hot cooked rice in a serving dish; spoon ham mixture over rice. Sprinkle with green onions, parsley, and tomato.