Prepare lemon marinade: Zest 1 washed lemon and squeeze the juice from 1-2 lemons (reserve 1 whole lemon for finishing). Finely chop 5 garlic cloves and mash with 1 teaspoon salt to form a paste. Remove the seeds from 1 chilli pepper and cut into small pieces. Mix all ingredients together and let stand for 1 hour.
Prepare spice mixture: Combine 1 teaspoon salt with paprika powder, cinnamon powder, coriander powder, and cumin powder.
Season the chicken: Carefully lift the skin on the 4 chicken drumsticks, rub most of the spice mixture onto the meat underneath, then pull the skin back down.
Prepare for baking: Brush a baking sheet with 2 tablespoons oil. Arrange the 4 chicken drumsticks skin side up on the sheet. Cut the 0.5 kg waxy peeled potatoes into chunks and quarter the 3 onions, then scatter them around the chicken. Sprinkle the remaining spice mixture over the vegetables.
Add liquids: Pour the marinade generously over the chicken and vegetables. Pour in 125 ml vermouth and 125 ml chicken broth. (If you prefer to avoid alcohol, substitute the vermouth with additional chicken broth.)
Bake: Bake in a preheated oven at 180°C (356°F) for 40-50 minutes until the chicken reaches 74°C (165°F) internally. Slice the reserved lemon and distribute the slices over the chicken and potatoes.