Preheat the oven to 500°F. Place the beets on a rimmed baking sheet and roast until the beets are completely charred and feel like soft butter when pierced with a knife, about 1-1/4 hours. Let cool.

In a small pan over medium heat, toast the cumin seeds until fragrant, about 5 minutes. Immediately remove the pan from the heat and stir until the seeds cool. With a spice grinder or mortar and pestle, grind the cumin to a powder (it’s fine if a few coarse bits remain).

Peel the beet skins with your hands or a paring knife, leaving a little of the char to add flavor. Cut into small cubes and toss in a mixing bowl with the salt, oil, cumin, and lemon zest and juice. Taste and adjust the seasoning.