Preheat the oven to 180C (fan)/Gas Mark 4. Slice the tops off the tomatoes about 1cm down from the stem (I like to keep the stems on). Scoop out the seeds with a teaspoon, but don’t worry about getting them all out. Drizzle a baking dish with the olive oil and place the tomatoes in the dish cut-side up, with the ‘lids’ cut-side down. Sprinkle with a couple of pinches of sea salt.
Bake for 15 minutes, or until slightly soft but still holding their shape. If they are really juicy inside, tip away some of the excess juice. Set aside while you make the crab stuffing.