Preheat oven to 425F (218C).
Line a large glass baking dish with foil.
In a bowl, toss tomato slices with olive oil, garlic powder, and sea salt.
Pour tomatoes into foil-lined glass baking dish. Try to lay each tomato slice flat.
Roast at 425F (218C) for 30-40 minutes.
Remove tomatoes from oven and let cool slightly. Turn off oven.
In a blender or food processor, combine egg whites, olive oil, and protein powder until smooth.
Reserve 8 tomato slices for the top of your focaccia, and put the rest in the blender along with the basil. Pulse or process until the tomato and basil are broken up into small pieces.
Pour mixture into a bowl, and mix in the psyllium husks. Let batter sit for 10-15 minutes to thicken.
Preheat oven to 325F (163C).
Pour batter into parchment-lined glass baking dish, 8"x11.5" (200mmx290mm) or slightly smaller, and spread evenly.
Place tomato slices on top.
Bake focaccia at 325F (163C) for 18-22min, until batter is cooked through.