Chickpea, apple and quinoa vegetarian burgers

Ingredients

• 400 gram can chickpeas, drained well
• 1 large apple, grated
• 1/2 cup cooked quinoa
• 1 egg
• zest of 1 lemon
• 1 tablespoon smoked paprika
• 1 teaspoon cumin seeds
• 1/2 teaspoon ground coriander
• 1 teaspoon sea salt
• gluten-free flour, for dusting
• lettuce
• 1/2 red onion, very thinly sliced
• cucumber, sliced thinly lengthwise
• sour cream
• 2 tablespoon capers
• squeeze of lemon juice
• 4 brioche buns