Place spareribs in a large saucepan and cover with water.

Add salt and cook, uncovered, over medium heat for 10 minutes.

Remove stalks from dried ancho chiles, slit them open, and remove veins and seeds.

Place chiles in a saucepan, cover with hot water, and simmer for 5 minutes.

Remove from heat and let soak for 5 minutes.

Place 1/2 cup of the soaking water in a blender.

Add garlic and cumin seed to the blender and blend thoroughly.

Add remaining 1/2 cup of water and some chilies, blending well.

Gradually add the remaining chilies, blending well after each addition.

Add the blended chili mixture to the meat in the saucepan.

Cut tomatillos into quarters, leaving the husks intact, and add to the pan.

Continue cooking the meat mixture, uncovered, until the meat is tender, the sauce is reduced, and fat floats to the surface (about 45 minutes).

The sauce should be thick and coat the back of a wooden spoon well.

Serve.