Mash tuna and water in a bowl with a fork to get clumps out, then liquefy in blender or food processor.
Add extra drops of water if needed to liquefy completely.
Pour into bowl and add flour and garlic powder; consistency should be like cake mix.
Spread into lightly greased baking pan; a round pizza pan or square cake pan works great.
Sprinkle with plenty of parmesan cheese.
Bake at 350° for 15 minutes; edges will pull away and texture will be like putty.
Use a pizza cutter and slice into small squares.
Let cool on a rack before serving. Store in an airtight container (or resealable freezer bag).