Discard any mussels that do not close after being rinsed.
Heat olive oil in a large pan over medium-high heat. Add chorizo and saute until it starts to brown. Add garlic, paprika, tomato paste, sugar, chili flakes and cumin. Stir well and cook 2 minutes more.
Add white wine, salt and pepper and lemon juice. Bring to a simmer, then add mussels. Cover and leave to steam for 5-7 minutes, until mussels open. Discard any mussels that do not open.
Transfer mussels to a serving dish and top with chopped cilantro and lemon zest. Serve with slices of crusty bread.