Preheat grill or broiler. In a small bowl, stir together butter, tomato paste, sherry vinegar, and salt; season with pepper. Set aside.Advertisement
Place bread on grill or under broiler until lightly toasted on both sides. Transfer to a wire rack; rub top of each slice with garlic, and let cool.
Using a small offset spatula, spread 1 teaspoon tomato butter on each bread slice; top with a ham slice. Using a 2-inch square cookie cutter or serrated knife, cut out squares. Spread a dab of tomato butter on ham; garnish with sun-dried tomato and oregano. Serve immediately.