4 chicken breasts, skin and bone removed
4 ripe tomatoes, each quartered
1 medium sweet onion, quartered
1/2 cup basil pesto
2 Tbsp mayonnaise
2 Tbsp butter, divided
Prepare the grill to medium-high heat.
Tear off 4 large sheets of heavy duty aluminum foil and place a chicken breast on each one.
Top each with the tomatoes and onion, evenly distributing each.
In a small bowl, whisk together the pesto and mayonnaise.
Spoon this mixture over chicken and veggies, then cut the butter into quarters and place a pat of butter on each.
Fold foil over tightly sealing them.
Put on grill on indirect heat, close cover, and cook for 20 to 30 minutes, spinning the packet around once during this cooking time.
Remove and let sit for 5 minutes before opening.