Smoky Tomato Spaghetti

Name: Smoky Tomato Spaghetti
Ingredients: 3 28-oz. cans whole peeled tomatoes, preferably San Marzano; 8 oz. smoked bacon (about 8 slices), finely chopped; 2 medium onions, peeled, halved through root ends; 2 medium shallots, peeled, halved through root ends; 10–12 garlic cloves, coarsely chopped; 1 7-oz. can chipotle chiles in adobo, chiles finely chopped, sauce reserved; 1 Tbsp. smoked paprika; 2 oz. basil (about half of a small bunch), plus leaves for serving; 1 tsp. Diamond Crystal or ½ tsp. Morton kosher salt, plus more; Freshly ground pepper; 1½ lb. spaghetti; 5 Tbsp. unsalted butter