Heat the oven to 375°F. Lightly grease 8 cups of a standard muffin tin with the cooking oil, using a brush or paper towel to coat the cups.

In a mixing bowl, combine the ground beef, egg, gluten-free panko, salt, half of the green onions, and 2 tablespoons of the teriyaki sauce. Mix gently until combined, taking care not to pack the mixture too tightly.

Divide the meat mixture among the 8 prepared muffin cups. Press it in lightly, leaving the tops slightly rounded. Brush the remaining 2 tablespoons of teriyaki sauce over the tops.

Bake for 20 to 25 minutes, until the meatloaf muffins are cooked through. Let them rest in the tin for 5 minutes before removing.

While the muffins bake, rinse the rice under cool water until the water runs mostly clear. Add it to a saucepan with the water and salt. Bring to a boil, then cover and reduce the heat to low. Cook according to the rice package directions, until tender and the water is absorbed.

Fold the drained pineapple chunks into the cooked rice. Cover the saucepan and let it stand for 5 minutes, then fluff the rice gently with a fork.

Serve the meatloaf muffins with the pineapple rice. Sprinkle the remaining green onions over the rice and muffins.