Preheat oven to 450°F (230°C).

Wash and core peppers, and slice in half.

Slice onion into thick half-moons.

Toss all vegetables with olive oil and spread onto lined baking sheet, keeping the peppers skin side up.

Bake until pepper skins blister but are not completely charred. Remove from oven and allow to cool.

Once cool, slide skins off pepper and slice into long strips. Season vegetables with kosher salt to taste.

Combine garlic, herbs, and spices for meat mixture in a large mixing bowl.

Gently incorporate ground beef until just combined, being careful not to overmix or meat will toughen.

Preheat grill and brush lightly with oil.

Form meat mixture into eight burgers and grill over medium heat for four to five minutes on each side. When flipping burgers, be careful not to pierce them, or juices will be released.

Split open burger buns and toast on grill, cut side down, for two minutes.

Combine mayonnaise and harissa in a small bowl and mix thoroughly.

To construct your sandwich, place a burger onto toasted bun.

Top with desired amount of harissanaise and grilled vegetables. Place remaining half of bun on top and enjoy!