Grilled Steak with Pepper Relish

Name: Grilled Steak with Pepper Relish
Ingredients: 3 small red, yellow and/or orange bell peppers, sliced; 1 small onion, halved and sliced; 2 tablespoons balsamic vinegar; 1 tablespoon extra-virgin olive oil; 1 tablespoon capers, rinsed; 1 tablespoon finely chopped fresh thyme or 1 teaspoon dried, divided; ½ teaspoon salt, divided; ½ teaspoon freshly ground pepper, divided; 1 pound sirloin steak or strip steak (1-1 1/4 inches thick), trimmed and cut into 4 portions; 1 teaspoon garlic powder