Place sweet potato slices in a mixing bowl and toss with 1 tsp. olive oil.
Spread sweet potato slices out evenly on baking sheets, giving each slice a little space.
Bake for 20 minutes. Flip to the other side and bake for 10 more minutes until golden brown.
Meanwhile, toss the tuna (AND tuna water), cherry tomatoes, garlic, basil, olive oil, lemon juice, and salt and pepper in a large mixing bowl.
When sweet potatoes are done, let cool.
Top sweet potato slices with tuna mixture, and enjoy!