Preheat the oven to 350 degrees F. Line a baking sheet with parchment paper and coat with nonstick cooking spray.
Coat 4 small bowls with nonstick cooking spray. Separate the eggs and put the whites into a medium bowl and the yolks in the small bowls (1 yolk per bowl). Add a large pinch of salt to the egg whites and beat with an electric mixer on low speed until stiff peaks form, 2 to 3 minutes.
Dollop 4 large spoonfuls of the egg whites onto the prepared baking sheet and make a small well in the middle of each with the back of a spoon. Bake the whites until they are firm, no longer wet and just beginning to brown, about 6 minutes. Gently pour 1 yolk into the well of each white. Bake until the edges of the yolk just start to set while still being runny, 3 to 4 minutes. Season with salt.
Serve on top of buttered toast.
Recipe adapted from: www.foodnetwork.com