1.Combine rind, chilli, garlic and oil in a large bowl with fish. Cover; refrigerate 3 hours or overnight.
2.Melt butter in a tagine or large frying pan; cook fennel, stirring, until browned lightly. Add beans, raisins, wine and saffron; top with fish. Bring to the boil. Reduce heat to medium-low; simmer, covered, 15 minutes or until fish is just cooked through. Season to taste.
3.Meanwhile, make red couscous. Heat oil in a medium saucepan over medium heat; cook harissa, paprika and half the green onion, stirring, for 2 minutes or until fragrant. Add stock and the water; bring to the boil. Remove from heat, add couscous; cover, stand 5 minutes or until liquid is absorbed. Using a fork, fluff couscous then stir in juice; season to taste. Top with remaining green onion.
4.Scatter nuts and reserved fennel fronds over tagine, then serve with red couscous.