Prepare the sofrito: Process all Sofrito ingredients in a blender until incorporated and finely chopped (just enough so that there are no large chunks).
Prepare the asopao: Heat oil in a large, heavy stockpot over medium-high. Add paprika, and cook, stirring constantly, until fragrant. (You can use more or less paprika, as desired.) Add Sofrito and tomato paste. Cook, stirring constantly, until very fragrant and slightly reduced, about 5 minutes. Add rice, and cook until slightly toasted, 1 to 2 minutes. Stir in 1 tablespoon of the salt. Add water, vinegar, and bay leaf. Bring to a boil; reduce heat to low, and cover. Cook until rice is almost tender, about 8 minutes.
While rice is cooking, season fish with remaining 1/2 tablespoon salt. Uncover stockpot, and nestle fish, shrimp, and tomatoes in rice. Cover and cook until rice and fish are fully cooked, about 7 minutes. Remove from heat, and let stand 5 minutes. Top servings with diced onion, chopped cilantro, lemon wedges, and jalapeño slices.
What to Drink
Pitorro, or Puerto Rican moonshine, is an ideal accompaniment for asopao. Described as "rum for tequila drinkers," this potent sugar cane-based spirit has traditionally been made in illicit backyard stills. But now, thanks to the Port Morris Distillery in New York, you can find legally bottled examples stateside. Port Morris's unaged Pitorro Shine is about as authentic as you can get and, even at 92 proof, remarkably smooth.