Preheat oven to 425 degrees. Scrub the sweet potatoes clean and slice lengthwise, to about 1/4 inches thick (use a mandolin if you have one).
Add sliced potatoes to a bowl and mix with 1 Tbsp. tallow, 1 tsp ground turmeric, and 1 tsp. ground ginger. Add sea salt to taste (I used about 1.5 tsp.)
Peel onions and slice very thin.
Add to a bowl with remaining tallow, turmeric, ginger, and sea salt.
Arrange potatoes and onions on individual baking sheets, and place in preheated oven with potatoes on the top rack. Bake for 20-25 minutes, rotating the sheets about halfway through. Remove when both the onions and potatoes are golden brown. Set aside to cool.
While they're cooling, slice avocados and radishes finely. Make a batch of Cilantro Mayo (click to get the recipe!)
To Assemble
Spread a thin layer of Cilantro Mayo on top of a crispy sweet potato slice. Top with a couple of thin slices of avocado, sliced onions, radishes, a sprinkle of sea salt and chopped, fresh cilantro.
Eat in one bite - the onions slide off if you don't!