Add all the ingredients - mayonnaise, ketchup, sriracha sauce, and paprika - to a mixing bowl and mix thoroughly.
In a medium sauce pan, add the soy sauce, beef stock, Mirin, and garlic, and bring it to a boil.
Mix the cornstarch with the water to make a slurry. Slowly whisk in the slurry.
Reduce it to low and let simmer for 10 minutes. Remove the garlic cloves before serving.
In a medium skillet, heat the olive oil over medium heat.
Season both sides of the tuna with salt and pepper.
Place the steaks in the skillet. Allow them to cook for only 1-2 minutes and turn over. Cook for only another 1-2 minutes.
Turn the steaks on their side and sear for about 30 seconds. Keep turning the steaks on their sides to sear all sides.
Top with the Soy Sauce Gravy, Spicy Mayo Sauce, and sesame seeds.
Toasted Sesame Seeds