Directions:

Preheat the oven to 425 degrees.

Scrub and dry the potatoes. Using the tines of a fork, pierce the potato several times. Place on the rack of the oven and bake until fork tender, about 1 hour.

Meanwhile, in a medium skillet over medium-high heat, heat the butter and oil until the butter melts. Add the onion, cook until softened and golden, 15-20 minutes. Add the tuna, cooking just until warmed through, about 3 minutes. Season with salt and pepper to taste.

Using a sharp knife, make a cross in the top of the potato and gently squeeze from the bottom to open the potato. Divide the tuna mixture evenly between the two potatoes, sprinkle with the feta and season with salt and pepper to taste. Serve immediately.