Coat a large griddle, outdoor grill rack or stovetop grill pan with cooking spray; preheat to medium-high heat.
In a large bowl, combine beef, salt, garlic powder, oregano, and red pepper flakes; divide mixture into 4 balls, then gently press each into a 4-inch patty.
Add tomatoes to pan and grill, flipping once, until grill marks are evident, about 4 minutes. Remove from grill pan and set aside.
Grill burgers, flipping once, about 5 minutes per side for medium (or to desired degree of doneness). About 2 minutes before the second side is fully cooked, evenly top each burger with Parmesan and cook until cheese melts.
Serve each burger on a toasted bun, evenly topped with tomatoes, 1 basil leaf, and 6 slices pepperoni.
Notes
Tips and Tricks
Do not overmix the beef - Mix the seasonings into the beef only until blended. Overmixing can make the burgers dense.Press the patties evenly - Shape the patties so they are the same thickness. This helps them cook at the same rate.Use a meat thermometer - Ground beef should reach 160°F for food safety.Toast the buns - Toasted buns hold up better under the burger, tomatoes, cheese, and pepperoni.
Storing and Reheating
Store in Refrigerator - Store cooked burger patties in an airtight container in the refrigerator for up to 3 days. Store buns, basil, tomatoes, and pepperoni separately when possible.Reheat in Skillet - Place the burger patty in a skillet over low heat. Warm until heated through.Reheat in Microwave - Place one burger patty on a microwave-safe plate. Heat in short intervals until warm.Freezer Storage - Freeze cooked burger patties without toppings for up to 2 months. Thaw in the refrigerator before reheating.