Melt butter in skillet; add onion, tomatoes and green pepper and cook over low heat until onion is soft. Stir in beef and cook until no pink remains. Remove from heat and stir in remaining ingredients. Cool.
Roll out pastry. Cut in 4" rounds. Place 1 tblsp. filling in center of each round. Brush edges with water and fold over dough, pressing edges together firmly. Cut steam vent in top of each.
Bake in hot oven (425°F.) until lightly browned, about 15 minutes.