To prepare the peppers: Place the pepper quarters under a hot grill, skin side up. Cook for about 5 minutes until the skin is black and bubbling. Remove and place in a small resealable bag to cool. When cool enough to handle remove the skin and cut each quarter in half.
To prepare the burgers: Heat a little oil in small pan over a medium heat. Add the onion and allow to cook for about 2-3 minutes until it has softened but not browned. Remove from the pan and allow to cool.
Place the mince, cooled onion, garlic, herbs, cumin, cinnamon and seasoning in a large bowl. Mix well. Using clean hands, shape mixture into four 2cm-thick burgers.
To cook the burgers: Heat a grill pan or barbecue to high. Brush a little over the grill pan. Add the burgers and cook for 4-5 minutes on each side. Remove from the heat and keep warm.
Cut the buns in half and lightly toast on the pan or barbecue.
To make the yogurt dressing: Cut the cucumber in half lengthways. Remove the seeds then finely dice the cucumber. In a small bowl combine the cucumber with the yogurt, cumin and lemon juice. Season and taste.
To assemble: Spread the bases of the toasted burger buns with some yogurt dressing. The top each bun with leaves, two pieces of pepper, a burger and another spoonful of the yogurt dressing. Serve any remaining dressing on the side. Delicious with potato wedges.