We took out some of the fat, but none of the flavor from this Tex-Mex dish.
Dust pork with cumin and oregano; season with salt. In a large nonstick skillet, heat oil over medium heat; swirl to coat bottom of pan. Add pork; cook until browned on all sides and slightly pink in the middle, about 8 minutes. Transfer to a cutting board; let rest 10 minutes before slicing thinly. Set skillet aside.
Preheat oven to 450 degrees. In a blender, puree salsa with 1/4 cup water until smooth. Add to skillet; cook over medium heat until warmed through, 2 to 3 minutes.
Warm tortillas according to package instructions. Assemble enchiladas. Top with heated salsa mixture and remaining 1/2 cup cheese. Bake until cheese is melted, 5 to 8 minutes. Serve immediately, garnished with tomato, if desired.
For a seafood variation, use one pound cooked shrimp instead of pork (skip step 1).