Bring ribs to room temperature; rinse and pat dry. Brush ribs all over with oil, then season with salt and pepper.
Move one of the racks to the bottom third of the oven and preheat to 325 degrees.
Heat a large Dutch oven or other heavy-bottomed pan over medium-high heat. Add ribs in one layer, preferably without touching each other, and sear for 2 minutes on each side or until lightly browned. Remove ribs and set aside; don’t clean out the pan!
With the burner turned off but while the pan is still hot, add onions and cook, stirring, until they stop sizzling.
In a large saucepan, stir together the tomato sauce, vinegar, sugar, Jalapeno pepper, garlic, mustard, cayenne pepper, cloves, and cinnamon. Bring to a boil, reduce heat, and simmer, stirring occasionally, for around 5 minutes. Turn off heat and stir in beer.
Nestle ribs among the onions, bone side up (fat side down), in one layer. Cover the pan, and bake until meat is very tender, around 2 to 2 1/2 hours.
Remove pan from oven and let ribs sit in sauce, covered, for 10 minutes.
Remove ribs to a serving platter. Spoon some sauce over the ribs, garnish ribs or platter with cilantro (if desired), and serve, passing additional sauce on the side.