Place the tuna steaks in a shallow dish and pour the 1/4 cup ponzu over them; let marinate for 10 minutes.
Heat 1 tablespoon olive oil in a skillet over medium-high heat until shimmering.
Remove tuna from the ponzu (reserve any excess if desired) and sear the steaks in the hot skillet for about 3 minutes per side for rare/medium-rare; the center should remain pink.
Transfer the seared tuna to a plate and set aside to rest briefly.
In a bowl, whisk together 1 tablespoon wasabi paste, 1 tablespoon water, 2 teaspoons minced fresh ginger, 1 tablespoon coconut cream, and 2 teaspoons coconut aminos until smooth.
Drizzle the wasabi cream over the seared tuna and serve over mixed greens or alongside preferred sides.