Prepare the sushi filling by combining the canned tuna, mayo, sriracha, and lemon juice in a bowl. Use a fork the break and fluff up the tuna. Set this aside.
Remove the end of a medium carrot and peel away the tough exterior. Use a vegetable peeler to peel thin shreds. Set the carrot aside as well.
Remove the ends of a cucumber (a seedless cucumber is best), but leave the peel on. Use the vegetable peeler to peel thin, wide, strips. Lay the strips flat on a clean surface, overlapping each piece halfway. Keep making cucumber peels until you have enough that creates an equal length to your nori seaweed sheet (about 2 ounces).
Press a paper towel against the arranged cucumber to remove excess moisture. Then, press the nori seaweed sheet flat against the cucumber.
Use a spoon to arrange half your tuna filling across the seaweed as pictured. Leave about a ½-inch space from all ends of the seaweed. Then, lay half the peeled carrots along the tuna.
In a gentle fashion, begin rolling the sushi by carefully pulling up the cucumber slices and tightly rolling them away from you. Use you fingers to tuck the roll into itself as you go along. When you’re done rolling the sushi, use a very sharp knife to slice approx. 6 pieces from your roll. Repeat these steps for a second sushi roll. Enjoy with freshly grated ginger!