handful of fresh coriander, chopped, plus extra to serve (optional)
salt and pepper
Use a 5 cm (2 inch) biscuit cutter to stamp out rounds from the tortillas; alternatively, cut them into wedges. Brush them with vegetable oil, place on a baking sheet under a preheated hot grill and cook for 1 minute on each side until crisp. Leave to cool.
Meanwhile, place the avocado flesh and crème fraîche in a food processor and blend until smooth. Stir in 1 tablespoon of lime juice and season to taste. Stir together the tomatoes, onion and olive oil, add lime juice to taste, season and stir through the coriander. Spoon a little of the avocado mixture on to each tortilla round, scatter over the tomato salsa and top with more coriander, if liked.