Spanish Prawns and Chorizo with Green Sauce

20 large, peeled raw prawns with tail on
2 long, soft-cured chorizo, sliced 1cm thick
Marinade
2 tablespoons tomato paste
1 teaspoon smoked paprika
2 cloves garlic, crushed
½ teaspoon cumin seeds
1 teaspoon dried oregano
finely grated zest and juice 1 lemon
2 tablespoons olive oil
sea salt and ground pepper
10 slim metal skewers or if using wooden, soak in cold water for 30 minutes to prevent them burning
Green Sauce
zest 1 lemon
2 tablespoons lemon juice
2 cloves garlic, crushed
1 teaspoon sea salt
pinch chilli flakes
½ cup packed herbs (I used parsley and basil)
1 teaspoon dried oregano
½ cup olive oil