Cook the pasta in a large saucepan of salted boiling water according to the packet instructions until al dente.
Meanwhile, put the chillies, coriander, garlic, almonds and lime juice in a food processor and process for 10 seconds. With the motor running, drizzle in the oil. Season with salt.
Heat a ridged griddle pan or heavy-based frying pan over a high heat until smoking. Add the tuna steaks and cook for 30 seconds on each side, or until seared but still pink in the middle. Remove from the pan and slice in half.
Drain the pasta thoroughly, then toss with two-thirds of the coriander sauce and divide between 4 serving plates. Top each portion with 2 pieces of tuna and a dollop of the remaining sauce. Serve with some lime wedges.