Pat the tuna steaks dry with paper towels, rub with olive oil, then sprinkle with garlic powder, onion powder, salt, and black pepper. Let sit for 10 minutes to absorb flavors.

Heat a large skillet over medium-high heat for 2 minutes. Sear tuna steaks for 3-4 minutes on each side until golden-brown and slightly rare in the center. Remove from heat at 130°F internal temperature.

In the same skillet, lower the heat and add butter to melt. Add minced garlic and cook for 30 seconds. Gradually pour in heavy cream, stirring, then add parsley, oregano, salt, and pepper. Simmer for 3-5 minutes.

In a large bowl, combine mixed greens, cherry tomatoes, and cucumber. Drizzle with olive oil and red wine vinegar, season with salt and pepper, and toss until well-coated.

Plate the tuna steaks, drizzle with creamy garlic sauce, and serve the salad alongside.