Preheat your oven to 200°C / 400°F. Grab a scissor and cut each one of your nori sheets into four equal squares.
Add the salmon cubes, sesame oil, soy sauce, garlic powder, smoked paprika, chili powder, half of the spring onion and salt together. Mix and set aside until ready to use.
To each nori square, add about 1 heaping tablespoon of rice and spread out slightly. Gently push the nori square in the muffin slot so that you center the rice in the middle with the edges coming up along the sides of the slot. Add a few pieces of cucumber, pushing them down firmly. Grab about 4-5 salmon cubes and fill each muffin slot. Bake for 15 minutes and then broil, if needed, at the end, to get a little tan on the salmon; about 1-2 minutes.
In a small bowl, mix the kewpie mayo, sriracha. honey and lime together.
Remove from the oven and allow to cool slightly before top with the spicy mayo, avocado, the remaining spring onion and sesame seeds.