Place oven rack 6 to 7 inches from broiler and preheat to high. Line a baking sheet or broiler pan with foil. In a large bowl, combine beef, pico de gallo, 1/4 tsp salt and 1/4 tsp pepper. Shape mixture into 4 equal patties, each 1/2-inch thick, and place on prepared baking sheet. Broil for 6 to 7 minutes or until burgers are browned. Flip and repeat on second side until burgers are firm to the touch and no longer pink in the center, 5 to 6 more minutes (internal temperature should read 160°F on a instant-read thermometer).
Place avocado in a small bowl and mash to a chunky consistency with a fork or potato masher. Add red pepper, cilantro, lime juice, garlic powder, pinch of salt and pepper, to taste; stir to combine.
To serve, spread 2 tbs yogurt on bottom half of each bun and top with 1 to 2 lettuce leaves, if desired. Then add patty and 3 tlbs avocado mixture to each before finishing with top halves of buns. Garnish burgers with additional cilantro, if desired.