Preheat grill.

In a small bowl, combine ingredients for the spicy BBQ sauce. Set aside until ready to use.

In a medium bowl, toss red onion rings with 1 tsp olive oil. Season with salt and pepper, set aside.

Remove the pulp from the tomato halves. Drizzle tomato halves with 1 tsp olive oil and season with salt and pepper.

Drizzle Foster Farms® Simply Raised® No Antibiotics Ever Free Range Chicken Thigh Fillets evenly with 1 tsp. Season with salt and pepper.

When ready to grill, add chicken thighs, tomato halves (cut side down), and onion rings to the grill.

Grill onion rings for 5 to 6 minutes, until slightly charred and soft, flipping halfway through. Grill tomatoes for 10 to 12 minutes, until soft and slightly charred, flipping halfway through.

Grill chicken for 3 minutes, then flip and baste with spicy BBQ sauce. Cook for another 2 minutes, then flip again and baste with BBQ sauce. Flip the chicken every minute for another 4 minutes, until the thickest part of the chicken has reached 165 degrees Fahrenheit, as read on a digital meat thermometer. Every time you flip the thigh fillets, be sure to baste them with more sauce!

To assemble the sandwiches, add a thigh fillet to each bottom half of the buns. Top with slices of red onion, then slices of avocado. Add one tomato half on top of each and top with more spicy BBQ sauce. Top with the other half of the bun and serve immediately.