Add the drained and rinsed tomatillos, fire roasted tomatoes with green chilies, lemon juice, lime juice, cumin, oregano, minced garlic and pepper to food processor.
Process until completely combined, about 10 seconds.
Add in the diced red onion, diced cilantro and pulse 2-3 times until just incorporated.
Taste and season with additional salt, if desired. I tend to add about 1 teaspoon of kosher salt.