I love this burger because of all its wonderful flavors! Marinated tomatoes, grilled onions, and a patty with sundried tomatoes, pairs deliciously with a sweet, rich, creamy Gorgonzola cheese spread. Mmmmm, these flavors bring to mind a marketplace café in Tuscany! This burger can be made indoors or on an outdoor grill.
In a large bowl, combine ground beef, sundried tomatoes (reserve oil for brushing on onion and bread), garlic, oregano, and kosher salt. Handling meat as little as possible, mix until combined. Form mixture into 4 patties to fit bun size. Cover; set aside.
In a medium bowl, add tomato slices, basil, balsamic vinegar, crushed red pepper flakes, and salt. Toss to coat. Let sit while preparing burger.
In a medium bowl, combine cream cheese, Gorgonzola, and chives until mixed.
Preheat large grill pan over medium high heat on stovetop. Brush 1 tablespoon reserved sundried tomato oil over red onions. Place onions on grill; grill 3-4 minutes, flipping once, or until grill marks appear. Place salami slices on grill pan; grill 3-4 minutes or until slightly crisp.
Grill hamburger patties, flipping once, 4-5 minutes per side or until desired doneness. Transfer patties to a plate; cover to keep warm.
Brush remaining 2 tablespoons sundried tomato oil over each cut side of bread. Place cut side down on grill; toast lightly, about 1-2 minutes.
To assemble burger: Spread Gorgonzola cheese spread over cut side of each bottom bun. Top each with arugula, a burger patty, salami slice, tomato slice, and red onion. Close each with a top bun. Serve immediately.