In a bowl, mix together the garlic, ginger, turmeric, cumin, coriander, garam masala, saffron, yogurt, lemon juice, and oil.
Add the shrimp, coating them well. Let marinate for 1 hour.
Preheat the oven to 450 F (230 C).
Remove the shrimp from the marinade, season with salt, and place on a greased baking sheet.
Bake in the oven for 4 to 5 minutes, or until they are lightly pink and slightly curved.
Remove immediately from the sheet and let cool.
Place on a bed of watercress and serve with basmati rice.