Make marinade sauce. In a bowl, mix together grated onion, 1 grated garlic, 4 tablespoons olive oil, 1 tablespoon yogurt, 1.5 tablespoon tomato paste, 1 teaspoon dried oregano, 1 tablespoon ground cumin, 1/4 teaspoon ground cinnamon. Put chicken thighs into the bowl and refrigerate for 1 hour.
In the meantime, make sauce. Preheat the oven broiler. Wash red bell pepper, pull the stems and remove seeds. Place red pepper on the baking sheet and broil. When dark splotches begin to appear on the peppers, remove the baking sheet from the oven and carefully turn each pepper over. When the tops of the peppers begin to darken again, remove them from the oven and place them into a bowl. Cover the bowl with plastic wrap and let cool. Once the peppers are cool enough to handle, peel the skin off.
Prepare cold water with some ice cubes in a medium bowl. Boil 1 cup water in a saucepan. Wash tomatoes and make a cross cut into the top of each tomato. When the water is boiled, put tomatoes. When the skin starts to peel off, take the tomatoes out of the saucepan and put them into cold water bowl. Peel the skin of tomatoes and chop.
Put chopped tomatoes and red bell pepper into a food processor. Puree until smooth. Transfer to a medium saucepan and add 1 grated garlic, 1 tablespoon tomato paste, 1 teaspoon dried oregano, 1tablespoon lemon juice, 1/2 teaspoon chili powder, 1/2 teaspoon salt and 1/2 teaspoon sugar to the saucepan . Heat over medium heat and simmer until it starts to boil. When it starts to boil, remove from the heat and let cool. When the sauce has cooled, stir in 2 tablespoons yogurt. Set aside.
Take the chicken thighs out of the refrigerator. In a skillet, cook chicken thighs until golden brown and cooked through. Add salt and black pepper to taste. Then place chicken thighs on each serving plate. Pour the sauce over the chicken thighs