In a bowl, combine soy sauce (or tamari), sesame oil, rice vinegar, lime juice, ginger, garlic powder, maple syrup, and sriracha. Toss the warm beets in this marinade, cover, and let sit in the fridge for at least 15 minutes, ideally 1 hour if you have the time. This is where the magic happens—the beets soak up all the umami flavors, transforming into a believable ahi tuna dupe.