Wash and dry all produce. Preheat toaster oven or oven to 400 degrees. Halve, peel, and thinly slice onion. Heat a drizzle of olive oil in a large pan over medium heat. Add onion and 1 tsp sugar. Cook, tossing, until browned, 6-8 minutes. Season with salt and pepper. Remove from pan and set aside.

While onion cooks, mince or grate garlic until you have 1/2 tsp (you may have a clove left over). In a large bowl, whisk together 1/2 TBSP tomato paste, 1 TBSP vinegar, 1 TBSP olive oil, and as much minced garlic as you like (we sent more tomato paste and vinegar than needed). Season with salt and pepper.

Wipe out pan used for onion. Heat a drizzle of olive oil in it over medium-high heat. Shape beef into 2 patties slightly wider than the bread. Season with salt and pepper. Add to pan and cook until just shy of desired doneness, 2-4 minutes per side. Sprinkle mozzarella on top. Cover pan and cook until cheese melts, 1 minute more.

Split ciabattas in half. Toast in toaster oven or oven until golden, 3-5 minutes. Meanwhile, halve tomatoes lengthwise.

Add lettuce, tomatoes, and cranberries to bowl with vinaigrette and toss to combine. Season with salt and pepper.

Fill ciabattas with beef patties, onion, and a few leaves from salad. Divide between plates and serve with remaining salad on the side.