Step 1

Preheat oven to 400 degrees F (200 degrees C).

Step 2

Season chicken thighs with salt and pepper.

Step 3

Melt 3 tablespoons butter in a large oven-proof skillet over medium-high heat. Place chicken skin-side down in the skillet; cook until browned, about 3 minutes. Flip and cook until second side is browned, 3 to 4 minutes. Transfer to a plate. Drain excess grease if desired.

Step 4

Heat remaining 1 tablespoon butter in the skillet. Add onion and garlic; cook and stir until fragrant, about 2 minutes. Stir in potatoes and red bell pepper; cook until tender, 5 to 10 minutes. Place chicken thighs on top.

Step 5

Mix sriracha sauce and brown sugar together in a bowl; pour evenly over chicken.

Step 6

Bake in the preheated oven until an instant-read thermometer inserted into the chicken reads 165 degrees F (74 degrees C) and potatoes are browned, about 30 minutes.