Do not substitute hot, half-sharp, or smoked Spanish paprika for the sweet paprika in the stew (see our recommended brands at right), as they will compromise the flavor of the dish. Since paprika is vital to this recipe, it is best to use a fresh container. We prefer chuck-eye roast, but any boneless roast from the chuck will work. Cook the stew in a Dutch oven with a tight-fitting lid. (Alternatively, to ensure a tight seal, place a sheet of foil over the pot before adding the lid.) The stew can be cooled, covered tightly, and refrigerated for up to 2 days; wait to add the optional sour cream until after reheating. Before reheating, skim the hardened fat from the surface and add enough water to the stew to thin it slightly. Serve the stew over boiled potatoes or egg noodles.
Adjust oven rack to lower-middle position and heat oven to 325º F.
Sprinkle meat evenly with 1 teaspoon salt and let stand 15 minutes.
Process paprika, roasted peppers, tomato paste, and 2 teaspoons vinegar in food processor until smooth, 1 to 2 minutes, scraping down sides as needed.
Combine oil, onions, and 1 teaspoon salt in large Dutch oven; cover and set over medium heat.
Cook, stirring occasionally, until onions soften but have not yet begun to brown, 8 to 10 minutes. (If onions begin to brown, reduce heat to medium-low and stir in 1 tablespoon water.)
Stir in paprika mixture; cook, stirring occasionally, until onions stick to bottom of pan, about 2 minutes.
Add beef, carrots, and bay leaf; stir until beef is well coated.
Using rubber spatula, scrape down sides of pot.
Cover pot and transfer to oven.
Cook until meat is almost tender and surface of liquid is 1/2 inch below top of meat, 2 to 2 1/2 hours, stirring every 30 minutes.
Remove pot from oven and add enough beef broth so that surface of liquid is 1/4 inch from top of meat (beef should not be fully submerged).
Return covered pot to oven and continue to cook until fork slips easily in and out of beef, about 30 minutes longer.
Skim fat off surface; stir in remaining teaspoon vinegar and sour cream, if using.
Remove bay leaf, adjust seasonings with salt and pepper, and serve.