1.Melt butter in a saucepan, then gently fry the capsicums and shallots. Add thyme, cook on low heat for 10 minutes or until softened.
2.Add the wine and vinegar, cook for a couple of minutes, then remove from heat. Stir in the green olives and caperberries, then fold in the basil. Season to taste.
3.Meanwhile, bring a pot of water to the boil. Toss in a few pinches of salt. Add the fusilli and cook for 8-10 minutes or until al dente. Add a few tablespoons of pasta water to the sauce, drain pasta, then fold pasta into the sauce.
4.Toss the tuna with the oil and season with salt and pepper. Heat a large frying pan until very hot. Toss in the tuna, fry for 10 seconds or so, until just cooked. Shake the pan thoroughly to loosen tuna from bottom of pan, then add the lemon juice. Mix with the pasta and serve.