Ingredients

• 25 Key limes
• ¹⁄₄ cup kosher or sea salt
• ¹⁄₃ cup canola oil
• 1 ¹⁄₂ tsp. brown mustard seeds
• ¹⁄₂ tsp. fenugreek seeds
• 20 fresh or frozen curry leaves
• 2 tsp. cayenne
• 1 tsp. ground turmeric
• ¹⁄₂ tsp. asafetida
• 1 cup fresh lime juice

Instructions

1. Using a paring knife, quarter Key limes lengthwise, leaving them attached by ½″ at the stem ends. Using your fingers, rub the limes inside and out with salt in a bowl. Transfer limes and salt to a 1-pint sterilized glass jar, packing them in tightly to fit. Cover jar with lid, and place jar near a window or any other spot indoors where it will receive a lot of sunlight and warmth; let the jar sit in this environment for 1 week, shaking the jar once a day to evenly disperse brine.
2. After limes have sat for 1 week, heat canola oil in a 10" skillet over medium-high heat; add brown mustard seeds, fenugreek seeds, and curry leaves, and cook, stirring, until seeds stop popping and spices are lightly toasted, about 2 minutes. Transfer to a spice grinder or small food processor, and process into a smooth paste. Stir in cayenne, turmeric, and asafetida. Mix spice mixture with lime juice, and then pour mixture into jar with limes; seal with lid. Shake jar to evenly disperse ingredients, and store in the refrigerator for at least 1 additional week to infuse flavors. Use for up to 1 year.