Combine all marinade ingredients in a medium bowl and whisk well. Add Tri-Tip Steak, toss to coat, and cover. Let marinate for 20-30 minutes.
Stir together mayo and sriracha sauce. Add lime juice and stir. Sauce should be a good consistency for drizzling. If not, add more lime juice or a few teaspoons of water as needed to thin it out.
Use tongs to transfer the marinated Tri-Tip to a grill preheated to high. (Discard marinade). Sear on each side about 2 minutes to get a good sear/grill lines. Reduce heat to medium and continue to cook 8-10 minutes until internal temperature reads 145 degrees F.
Remove from grill, allow to rest about 5 minutes. Slice across the grain, then drizzle with teriyaki sauce and spicy mayo. Serve immediately.
Teriyaki sauce:my homemade teriyaki sauce has no "weird" ingredients, is ready in just 10 minutes, and tastes SO good. You'll only need about half of a batch, so you can either half the teriyaki sauce recipe, or make the full batch and then store the rest in the fridge or freezer for later (my favorite method!).