I love spicy tuna rolls but I didn’t feel like making them for a pot luck at the Fort Worth Japanese Society.  I had a thought about making them in the form of tossed sushi and calling it “Spicy Tuna Chirashi-zushi”.  When I goggled it, sure enough it was already done by someone else.  There are, after all, very few original ideas left.  No problem, I had my own version in mind and that is what I made.  This makes a very large amount, enough for 10-12 servings, so reduce it in half or even make a smaller amount and make 2 bowls, 1 portion each.
I picked up a pound piece of big eye tuna, sushi grade, at Central Market.  You have to ask for it at the seafood counter and they keep it frozen in the back.  It’s about $20.00 per pound.  Always use frozen fish for sashimi or sushi!  Keep it frozen until you are going to use it, then run cold water over it while it’s still in the package.  Don’t defrost it completely before you cut it.  Once you cut it, keep it cold, on a chilled plate, on ice, etc. The “fresh” fish you see in the case may have the same name, i.e., tuna, salmon, etc. but it is not for sushi.  You must sear it if you want to eat it rare and never eat it raw. 
Start with really great rice, short grain sushi rice, in the bulk section at Central Market is fine, or buy a bag of high quality Japanese rice.  I use Hitomebore, which I bought recently at H Mart in Houston.
I use an electric rice cooker, a Zojirushi fuzzy logic type, expensive but well worth it.  Perfect rice every time! 
3 cups rice–rinsed well, until the water is almost clear
3 cups water
Allow rice to soak for 20 minutes.
Cook in a heavy pot over medium heat for 10 minutes, reduce to very low and cover with a tight fitting lid.  Cook another 10 minutes or longer, until the rice is completely transparent.

Sushi Vinegar
5 T rice vinegar
1 1/2 tsp sea salt
2 T sugar
Whisk ingredients together is a small bowl.
Place hot rice in a large bowl and add sushi vinegar.  Gently mix, turning the rice over until each grain looks plump and the vinegar has been absorbed.  Fan the rice for about 30 seconds to give it a glossy appearance.  Let it cool covered with a moist kitchen cloth to keep it from drying out.

1 pound big eye tuna, cut into even 1/2 inch pieces
2 avocados cut in 1/2 inch pieces
1 piece nori, roasted over a gas flame, or electric burner to re-crisp, then cut into very thin 2″ strips with scissors
1/2 cup seasoned mayonnaise * 
1/4 cup Sriracha
1/4 cup finely chopped chives

*Seasoned Mayonnaise
1/2 cup mayonnaise
1 T rice vinegar
1 tsp sugar
1/2 tsp salt
1 T lemon juice
Mix above ingredients together.  Place in a squeeze bottle with a small tip.

Arrange 1/2 the sushi rice in a large shallow, attractive bowl.  Place 1/2 the cut up tuna and avocado on top of the rice.  Sprinkle with the seaweed.  Drizzle with mayonnaise and sriracha in alternating lines.  Place the rest of the rice on top and repeat, ending with sprinkled chives. Sprinkle toasted sesame seeds on top or tokibo (flying fish roe), if you are lucky enough to have some!

This was very popular at the potluck and several older Japanese women told me how much they enjoyed my “tuna rice”.  My mother would have been very pleased.