preheat oven to 400

in a med. ovenproof skillet, heat oil over med-high heat

in a lg. bowl, stir together the potatoes and onion. transfer the mixture to the skillet. Using a spatula, gently spread and press it into an even layer. Reduce the heat to low. cook, covered, for 10-12 min. or until the potatoes are just tender

meanwhile in a lg. bowl, whisk together the eggs, cheese, and pimiento. Pour over the potato mixture. don't stir. bake 10-15 min. or until tortilla is set.