First make the tuna salad. Combine the tuna, yogurt, Dijon and hot sauce in a bowl. Add some salt and pepper and mix everything together. Taste to adjust any necessary seasonings. You can add more hot sauce if you like things spicy.
Lightly toast the sourdough in a toaster for 2-3 minutes. You don’t want it to have any color at this point but to be a bit crisp around the edges.
Place half of the tuna salad mixture on one piece of the bread. Add 2 slices of tomato on top and then a piece of cheddar cheese.
Put the bread on baking sheet and repeat with the other slice.
Broil the tuna melts for 3-6 minutes until the cheese is melted and starting to bubble up.
Top the melt with some fresh chopped basil and enjoy!