Rinse the lentils in cold water. Bring 1.5 cups of water to the boil and add the lentils. Reduce to a simmer and cook for 10 minutes or until cooked through. Drain away any excess liquid and set aside to steam dry.
Add the diced sweet potatoes to a small pan of boiling water. Simmer for 5-6 minutes or until fork tender. Drain completely and set aside to steam dry.
Whilst the lentils and potatoes cook, heat half a tablespoon of coconut oil in a frying pan over a low/medium heat. Add the garlic and onion and sweat gently until tender then set aside to cool.
Add the sweet potato to a mixing bowl along with the lentils, garlic and onion, paprika, cumin, chilli powder, oregano, lemon zest, tahini, salt and pepper. Stir to combine then mash together well.
Divide the mixture with your hands into ten even portions, roughly a tablespoons worth, and shape into individual patties about 2 inches wide.
Heat the remaining coconut oil in the frying pan used to cook the onions over a medium heat.
Once hot, add the patties to the pan – you can do this in batches if required. Cook for 3-4 minutes each side or until hot through, crisp and golden.
Whilst the patties are cooking whisk together the dressing ingredients.
To serve, place each patty on a lettuce leaf and top with a layer of tomato and red onion.
Top each with a teaspoon of dressing and a further lettuce leave to finish.