Zest and juice the lemons, grate the garlic and ginger, cube or crumble the feta or purchase pre-crumbled, crush the pistachios in a ziploc bag with a rolling pin or mallet, julienne the red onion, and slice the watermelon or purchase pre-sliced. Mise en place the remaining ingredients and get a large 4-qt bowl for the salad and 2-qt bowl for the vinaigrette.
If using xanthan gum add it and the black pepper and salt to the 2-qt bowl and whisk to combine. You want to ensure the xanthan gum is fully dispersed throughout the salt and pepper to prevent clumps in the vinaigrette. If not using xanthan gum just add the salt and pepper to the bowl and move on to the next step.
Next add the lemon juice, white wine vinegar, grated garlic, grated ginger, course ground mustard, honey and microplaned lemon zest to 2-qt bowl and whisk thoroughly to combine.
Next stream in the extra virgin olive oil as you whisk until it is fully incorporated. If you used xanthan gum the vinaigrette should appear homogenous, opaque and fully emulsified.
In the 4-qt bowl add the baby arugula, watermelon, crushed pistachios, cubed or crumbled feta, julienned red onion, a few pinches of salt, some freshly cracked black pepper and the ginger lemon vinaigrette to the bowl. Thoroughly toss to combine. Serve immediately.