Crab & avocado tostadas - Good Food Middle East

Ingredients

• 1 small red onion, sliced into thin rings
• juice 2 limes, plus wedges to serve
• pinch of caster sugar
• 170g can white crabmeat in brine, drained
• 2 spring onions, finely sliced
• 1 red chilli, deseeded and chopped
• 1 really ripe avocado, peeled, stoned and chopped
• 1 small garlic clove, crushed
• 2 corn tortillas
• handful mixed salad leaves