Black bean falafel

Ingredients

• 2 x 400g can black beans, drained and rinsed
• ½ onion, diced
• Large handful fresh coriander
• 1–2 cloves garlic
• 1 teaspoon cumin
• ½ ­–1 teaspoon chilli powder (optional)
• ½ lime, juice only
• Freshly ground black pepper, to taste
• 1 tablespoon rapeseed oil
• 4 wholemeal pita breads, warmed
• 160g little gem lettuce, washed and shredded
• 2 medium tomatoes, diced
• 10cm cucumber, diced
• 4 teaspoons tahini