In a small bowl, whisk the mayonnaise, sour cream, ketchup, water, vinegar, relish, onion, sugar, Tabasco, and 1/8 teaspoon salt. Set aside.

Heat the oil in a large skillet over medium. Add the onion and saute for 2 minutes, stirring frequently.

Add the ground beef and cook for about 6-7 minutes, stirring occasionally and using the spatula to crumble the meat.

Add the garlic and stir constantly for 30 seconds, until fragrant. The meat should no longer be pink; if it is, continue to cook until browned. Remove pan from heat and set aside while you assemble the salads.

Divide the romaine, tomatoes, and cheese evenly among four large bowls or plates. Divide the beef mixture evenly among the salads. Drizzle each serving with 2 tablespoons dressing. Serve immediately.