Combine all spices and stir to mix equally. Set aside.
Preheat water bath to 132 degrees.
Rub tri tip very generously with spice rub mixture on all sides.
Vacuum seal or use the water displacement method (with ziplocs) to bag the tri tip.
Cook at 132 for 6.5 hours. (Anywhere from 6-12 hours will produce a good result. If you need to leave it in a little longer than 6.5 hours, don't stress! It'll still be great!).
Remove from bag and dry tri tip extremely well.
Spread a very, very thin layer of mayo onto the tri tip (I like to use a silicone pastry brush for this).
Heat a large cast iron skillet over medium high heat until VERY hot.
Add avocado oil and then the tri tip. Sear for about 30 seconds on each side until well browned.
Remove from pan, slice and finish with smoked Maldon salt.