Corned Beef with potatoes

1 tbsp vegetable oil 2 small potatoes , diced 1/2 lb corned beef , thinly sliced across grain 1 tsp spices that come with corned beef 1/2 tsp red pepper flake[...]

2 lbs potatoes , peeled and cut into pieces 1/2 tablespoon oil 1 large onion , peeled and chopped 12 ounces can corned beef 14 ounces can peeled tomatoes salt[...]