This dish is so simple I feel silly even describing it. There are no new techniques and no new ingredients, but the dish is quick and tasty and is an unusual way to use cheese.
Queso in Salsa comprises a cheese, one of the non melting ones, panela is easiest but queso fresco can be used too. The cheese is served in a tomato sauce, and as these cheeses don't melt the end result looks like cubes (in the case of panela) or blobs (in the case of queso fresco) of tofu suspended in sauce.
The tomato sauce is made as we have seen in lots of other dishes (rajas con queso for example), simply tomatoes, blitzed to a liquid in a blender and then cooked out, with some onion, garlic, chile, oregano and seasoning. Rather than adding the onion to the blender it can be cut into strips and sautéed with the chile until translucent before adding the tomato.
Tinned tomatoes can be substituted for fresh, and personally I prefer not to blend the chile with the tomatoes and I feel it muddies the nice red colour, though I'm probably just being picky.
Once the sauce has cooked out the cubed panela is added and heated through. At some point in the future I'll go into more detail on Mexican cheeses, there quite a bit to discuss. I've actually made queso fresco once or twice using milk and vinegar or milk and lime juice. It's fun to do and in interesting experiment, though I don't think I'll be breaking out the cheese cloth on any regular basis.
The dish can be eaten with tortillas or served like a soup. Easy!