Hamburgers With Mustard Butter

• 2 tablespoons unsalted butter, softened
• 2 teaspoons Dijon mustard
• 2 plum tomatoes, diced
• 1/2 red onion, diced
• 1 1/2 pounds ground beef
• 4 romaine lettuce leaves
• 4 hamburger buns
• 1 1/2 teaspoons salt
• Freshly ground pepper to taste

1. Combine butter and mustard until smooth.
2. Chill until semifirm.
3. Toss together tomatoes and onion.
4. Start a charcoal grill.
5. Divide the beef and mustard butter into 4 four equal portions.
6. Press butter into the center of each piece of beef and form a ball around it.
7. Gently flatten into a patty.
8. Grill to desired doneness.
9. Place a lettuce leaf on the bottom half of each bun and top with a patty.
10. Season the meat with the salt and pepper.
11. Top with the tomato mixture and bun tops.
12. Serve immediately.

unsalted butter, mustard, tomatoes, red onion, ground beef, buns, salt, freshly ground pepper

Taken from cooking.nytimes.com/recipes/2991 (may not work)