Put the bacon and cherry tomatoes, cut side up, on a grill rack and grill for 10 mins, turning the bacon halfway through, until crisp. Meanwhile, roughly mash the avocado with a fork and stir in the lime juice, chilli flakes, some salt, if you like, and pepper.
Toast the bread until golden and spoon on the mashed avocado. Top with the tomatoes and bacon, then serve.