Tear off a 2-ft section of parchment paper and lay it on the counter for the walnuts when they're done. In a large skillet, spread walnuts out over the bottom of the pan and toast over med-high heat for 1-3 minutes until browned in spots.
Add the butter and continue to brown the walnuts 1-2 minutes more. Slide skillet off the heat and pour syrup evenly over the walnuts (it should sizzle when it hits the hot pan).
Slide the skillet back onto the burner and cook over med-low heat enough to make the maple syrup gently bubble for about 2 minutes, while stirring. The syrup should thicken and coat the walnuts.
Pour the candied walnuts out onto the parchment paper, separating any that stick together. Immediately sprinkle with salt and Chipotle chile powder, to taste. Allow to cool about 20 minutes. The maple coating will harden as it sits.
For the Orange-Dijon Dressing:
Zest the orange first. Hold the orange and grapefruit over a bowl while carving out segments to capture extra juice—use juice in dressing.
Prepare dressing by mixing the ingredients in a cruet or jar with a lid and shake. Refrigerate for 5-10 minutes before serving.
Building the Salad:
Rub the torn kale with a little oil and salt, set aside.
Gently mix the grapefruit, oranges, and fennel in a salad bowl. Fold in the kale, feta, and walnuts with enough dressing to lightly coat.
Garnish with pomegranate arils, and serve immediately.
Notes
The dressing will cause the citrus to release its juices a little, so if the dressing will be on the salad for more than 30 minutes before serving, use a little less dressing. Any added juice from the citrus will incorporate by tossing gently again just before serving.