Preheat a grill or pan to medium-high heat.

Season the ground beef with salt and black pepper, and form into 4 equal-sized patties.

Grill the patties for about 3-4 minutes on each side, or until they reach your desired level of doneness.

Place blue cheese on top of each patty for the last minute of cooking to allow it to melt.

Lightly toast the burger buns on the grill or in a pan.

Assemble the burgers by placing a lettuce leaf, a slice of tomato, and the blue cheese-topped patty on the bottom bun. Cover with the top bun.

For the salad, halve the cherry tomatoes, slice the cucumber and bell pepper, and thinly slice the red onion.

In a large bowl, combine the mixed greens, cherry tomatoes, cucumber, bell pepper, and red onion.

In a small bowl, whisk together the olive oil, red wine vinegar, Dijon mustard, salt, and black pepper to make the dressing.

Drizzle the dressing over the salad and toss gently to coat.