Preheat barbecue or chargrill pan on high. For salsa: combine tomatoes, onion, lime rind and juice, chilli, avocado,coriander and oil in a bowl. Taste and season with salt, pepper and sugar.
Combine paprika and oil in a medium bowl. Add chicken and season with salt and pepper. Gently toss to combine. Cookchicken on barbecue or chargrill pan, turning occasionally, for 8-10 minutes or until browned and cooked through. Placechicken on an oven tray, cover with foil and set aside in a warm place.
Warm burritos on barbecue or chargrill pan until lightly charred.
Place burritos on serving plates. Top with chicken and spoon over salsa. Add watercress and a dollop of yoghurt.