Stir together the passata, the rind and juice of the orange and lime, the tequila, if using, and Worcestershire and Tabasco sauces in a non-metallic bowl and season to taste. Add the spring onions, tomato, cucumber and prawns and mix together. Cover with clingfilm and leave to marinate in the refrigerator for 30 minutes.
When ready to serve, stone, peel and slice the avocado, then place in serving bowls or plates with the lettuce. Spoon over the prawn mixture and scatter with coriander leaves. Serve with saltine crackers or tortilla chips.