Turn oven onto a low broil
On parchment lined cooking sheet, place sliced onion, sliced bell peppers, sliced Serrano peppers (leave in seeds for more heat, removed seeds for less heat) and sliced tomatoes with insides removed (save for later, will be added back in).
Sprinkle everything with a generous helping of salt and pepper.
Roast in over for 15-20 minutes, or until edges of veggies are browned.
Place roasted veggies in a food processor, add the pummelo juice, tomato insides, Sazon seasoning and cilantro. Blend on low until well chopped.
Serve with fresh tortilla chips!
Makes approximately 16oz of salsa