Grilled chicken with sweet peppers

Ingredients

• 1 1/2 tsp garlic powder
• 1 1/2 tsp paprika
• 1/2 tsp salt
• 1/2 tsp freshly ground black pepper
• 1/4 tsp cayenne pepper
• 8 skinless, boneless chicken thighs , or 4 skinless, boneless chicken breasts
• 1 green bell pepper
• 1 red bell pepper
• 1/2 small red onion
• 1/2 pint cherry tomatoes , or 2 plum tomatoes
• 1/4 cup balsamic vinegar
• 1 tbsp olive oil
• 1/4 tsp salt