How to Make It
In a bowl, combine the garlic, lemon and lime juices, orange and lemon zests and cayenne pepper and let stand for 10 minutes. Stir in the olive oil and season with salt.
In a skillet, toast the cumin and caraway seeds over moderate heat until fragrant, about 1 minute. Let cool completely, then grind coarsely in a spice mill or mortar.
In a bowl, toss the ground spices with the beets, scallions and jalapeño. Add the dressing and toss again to coat. Season with salt. Spread the arugula on a platter. Mound the beet slaw on top and serve.
To julienne beets, use a mandoline or the shredding disk of a food processor.