Combine 1 tablespoon (15 ml) water and 1/2 teaspoon (2.5 ml) baking soda in a small bowl. In a large bowl, toss beef with baking soda mixture and 1/2 teaspoon (2.5 ml) salt until thoroughly combined. Set aside.
Heat oil in a 12 inch (30 cm) non-stick skillet over medium heat until shimmering. Add onion and remaining 1/8 teaspoon (0.5 ml) baking soda and stir to coat. Cook, stirring occasionally, until onion is softened, 3 to 4 minutes. Add garlic and cook, stirring constantly, until fragrant, about 30 seconds. Stir in sugar, paprika, pepper flakes and remaining 1/8 teaspoon (0.5 ml) salt and cook, stirring constantly, until paprika is fragrant, about 1 minute. Add tomato paste and cook, stirring constantly, until paste is rust-colored, 3 to 4 minutes.
Add beef and cook, breaking up meat with a wooden spoon, until beef is no longer pink, about 5 minutes. Mash beef with a potato masher until fine-textured, about 1 minute. Add ketchup, vinegar and Worcestershire and stir to combine, scraping up any browned bits.
Combine cornstarch and the remaining 1 tablespoon (15 ml) water in small bowl, then pour the cornstarch mixture over the beef and stir to incorporate. Cook, stirring constantly, until the sauce thickens and coats the beef, about 1 minute. Season with salt, extra sugar, and extra vinegar to taste. Spoon the beef mixture onto buns and serve.
