Tear large pieces of cabbage. Rinse and pat dry.
Over medium heat in large cast iron skillet, add a light layer of coconut oil to coat pan. Place grapefruit halves and slices face down. Sauté for 3-5 minutes or until lightly charred. Add additional coconut oil as needed to prevent from sticking. When grill marks evenly appear, remove from heat. Set aside.
In same skillet, still over medium heat, toss cabbage and torn tarragon leaves every few seconds to lightly char for a few short minutes. Remove from heat. Set aside to cool.
Part 3, same skillet, same temp: add 2-3 tablespoons of coconut oil, melt. Toss in chopped macadamia nuts. Sauté for 2-4 minutes or until lightly browned and fragrant. Remove from heat and set aside.
Prepare dressing: In a small bowl, whisk oil, squeezed grapefruit juice, vinegar, mustard and honey. Season with salt. Store any leftovers in an airtight jar in the fridge. Lasts several weeks.
Prepare salad: In large salad bowl, add cabbage and tarragon, arugula, sliced apples. Toss with vinaigrette, amount to your preference. Top with optional slices charred grapefruit and toasted nuts. Serve immediately.