Heat oven to 400° F.
Heat 1 tablespoon of the oil in a large, preferably ovenproof skillet over medium heat. Add the onion and cook until softened, about 3 minutes. Add the garlic and jalapeño and cook for 1 minute. Remove from heat; let cool.
In a large bowl, combine the pork, bread crumbs, egg, salt, pepper, cumin, and onion mixture. Shape into 12 meatballs.
Wipe out skillet, add the remaining oil, and heat over medium-high heat. Brown the meatballs on all sides, about 7 minutes total.
If not using an ovenproof skillet, transfer the meatballs to a baking dish. Pour the salsa over the top. Bake until cooked through, about 25 minutes.
Tip: If you're in the mood for soft tacos, set out corn or flour tortillas and shredded cheese with the meatballs. Otherwise simply serve them over rice.