Place pine nuts on a baking sheet and toast in oven for 5 minutes or until browned.
Roughly chop olives and parsley. Finely mince garlic and halve tomatoes. Zest the peel of the lemon and reserve the rest.
In a large saute pan, heat butter and 2 tbsps olive oil over medium-high heat. Lightly season swordfish on both sides with salt and fresh ground black pepper.
When butter and olive oil start to smoke slightly, add swordfish. Sear 2 minutes on each side.
Cover saute pan, turn heat to medium-low, and let cook for 5 minutes. Remove from heat and let rest.
In a separate small saute pan, add 1 tbsp of olive oil. Saute garlic for 1 minute. Add pine nuts, olives, capers, tomatoes and lemon zest. Cook over medium to medium-low heat for 5 minutes or until tomatoes soften. Gently stir to ensure there is no burning.
To plate, top swordfish steaks with puttanesca sauce. Sprinkle with fresh parsley and a squeeze of the reserved lemon.