Pat the tuna steaks completely dry with paper towels and season both sides evenly with sea salt and black pepper.
Heat the extra virgin olive oil in a cast-iron skillet over medium-high heat until it begins to shimmer.
Place the tuna in the hot skillet and sear for approximately 1 to 2 minutes per side for a rare to medium-rare interior.
Remove the tuna from the skillet and set it aside on a cutting board to rest for 3 minutes.
In the same skillet, reduce the heat to medium and add the toasted sesame oil, grated ginger, and minced garlic, sautéing for 30 seconds until fragrant.
Add the zucchini noodles and tamari to the skillet, tossing constantly for 2 minutes until the noodles are just tender but still retain a slight crunch.
Slice the rested tuna against the grain into thin strips.
Divide the zucchini noodles between plates, top with the sliced tuna, and garnish with black sesame seeds.