Combine your chopped lemon peel with salt in a clean, dry glass container. Mix thoroughly to ensure every piece is coated. Leave the container at room temperature, stirring a couple times daily. You'll notice liquid beginning to pool at the bottom—this is exactly what you want.

Stir in the turmeric, making sure it's evenly distributed throughout the lemon mixture. The peels will take on a gorgeous yellow-orange hue. Continue leaving at room temperature, stirring once daily.

Toast the fenugreek in a dry pan over medium heat until fragrant and slightly darkened. Let cool, then grind to a powder using a spice grinder or mortar and pestle.

Heat 3 tablespoons of your oil in a small pan. Add the black mustard seeds and cook until they begin popping energetically. Reduce heat to low, add the chili powder, and stir for 1-2 minutes to bloom the spices. Remove from heat.

Add the ground fenugreek and asafoetida (if using) to your lemon mixture and stir well.

In a separate pan, heat the remaining oil until it reaches approximately 350°F (177°C)—it should just be starting to smoke. Carefully pour this hot oil over the lemon and spice mixture. Pack into jars and top up with more oil if necessary. The oil should sit above the solids.

Stir everything together and allow to cool completely.