Cut onions into ½ inch-thick rings. Keeping the rings together.
Skewer onion slices with two skewers, making sure the skewers are spaced about one inch apart.
Brush each onion slice with olive oil and season evenly with salt.
Prepare the grill for direct medium heat, 350°F to 450°F.
Grill the onions over direct heat until blackened and seared by the grates approximately 8 to 10 minutes, flipping once halfway through cooking.
Carefully remove the onion rings from the skewers and serve.
