Combine all your ingredients together for the tuna marinade. Whisk together and place to the side for a quick moment.
Pat your tuna steaks dry and place them in a container for marinating. Add in the marinade and mix well. Seal and place in the fridge for a minimum of 4 hours.
When you get your tuna steaks in the marinade go ahead and start prepping your pineapple salsa. Earlier the better because you want the salsa to sit for a few hours in the fridge, this will allow the ingredients to blend well for enhanced flavor.
Create the salsa by adding all the prepped salsa ingredients into a larger mixing bowl and stir with a wooden spoon. Make sure to stir well.
Place the salsa in the fridge and patiently wait.
Now that your 4 hours has expired, start your charcoal because you want to have a blazing hot cast-iron surface for a quick tuna steak sear.
Remove the tuna steaks from the marinade and keep them on the steaks so it acts as a binder, add the toasted sesame seeds on top and bottom.
Use a flat top cast iron griddle and get it up to 500-550 degrees. Coat with avocado oil for searing.
Place the tuna steaks once the surface is 500-550 degrees and sear for 1 min per side. You can push to 1 min 30 seconds but this tuna is sushi-grade and safe to eat raw.
Remove the tuna steaks and slice for serving, plate and add your pineapple salsa.
Serve and enjoy with family/friends!