Put a large non-stick frying pan on a medium-low heat. Trim the fennel, pick and reserve any leafy tops, then halve the bulb and finely slice it. Place in the pan with 1 tablespoon of olive oil and cook with the lid on for 5 minutes. Meanwhile, cook the pasta in a pan of boiling salted water according to the packet instructions, then drain, reserving a mugful of cooking water.
Deseed and finely slice the chilli, stir into the fennel pan and cook uncovered until soft and sticky, stirring occasionally. Halve the tomatoes and toss into the pan for 2 minutes, followed by the crabmeat and, 1 minute later, the drained pasta. Loosen with a splash of reserved cooking water, if needed, then season to perfection with sea salt and black pepper, sprinkle over any reserved fennel tops and drizzle with 1 teaspoon of extra virgin olive oil. Enjoy.