Combine the dressing ingredients (olive oil, both vinegars, garlic powder, basil, salt, pepper) in a bowl. Add kale, beets, and red onion. Let marinate in the fridge for at least 10 minutes while you prepare the salmon. Add tomatoes just before serving.
Whisk the salmon marinade together and coat the fillet.
Heat a pan to medium and place the salmon in. Sear 3–4 minutes per side until cooked through.
Plate the salad, top with the cooked salmon and crumbled feta, and serve.