Step 1

Preheat oven to 425°. Toss rutabaga with 3 Tbsp. oil on a parchment-lined rimmed baking sheet; season with salt. Roast, tossing once halfway through, until golden brown and tender, 15–20 minutes.

Step 2

Meanwhile, heat remaining 2 Tbsp. oil in a large skillet over medium. Add onion and cook, stirring occasionally, until slightly softened and golden brown, 8–10 minutes. Add kale, red pepper flakes, and ⅓ cup water and cook, stirring occasionally, until kale is tender but still bright green, about 3 minutes. Add rutabaga, season with salt, and toss to combine.

Step 3

Toss watercress with lime juice in a small bowl; season with salt.

Step 4

Divide rutabaga mixture among tortillas. Top with watercress mixture and queso fresco. Serve with hot sauce alongside.