Start by making the pickled red onions. In a bowl, add in thinly sliced red onion, plus the water, lemon juice, and salt. Stir the onions so that they're all coated, then let rest while you make the rest of the salad (or for at least 15 minutes).
Then, make the vinaigrette. Combine all vinaigrette ingredients into a bowl and whisk together.
Prep your curly kale by removing any large pieces of the stem, then chopping the kale into bite-sized pieces.
Toss the kale with the vinaigrette with your hands, mixing it so that the kale pieces are entirely coated.
Then, add in the rest of the ingredients (including the marinated red onions). Top off the salad with the sunflower and pumpkin seeds last (so they don't go to the bottom).
Enjoy!