In a large bowl, rub lemons with salt and turmeric, pack into a sterilized 1-qt. glass jar. Cover with lid and place on your counter or near a window with direct sunlight. Let sit 1 week, shaking jar daily to disperse brine.
After 1 week, heat oil in a 10"skillet over medium-high heat; cook mustard, cumin and fenugreek seeds until they pop, 1-2 minutes.
Add chiles, garlic and ginger; cook until golden, 4-6 minutes. Stir in vinegar, sugar, and chile powder.
Pour over lemons; reseal lid, shake to combine and chill 1 week to infuse flavors. Enjoy.