Duck with Oranges

Salt the duck breasts and rub them with black pepper. Put them to sear on both sides in the butter and oil. Remove the meat and, in the same pan, add the chopped onion to fry. Squeeze the juice from the oranges and add it to the onion. Cut the peel of 1 orange into large pieces and add it too. Pour in the lemon juice, the red wine and the marmalade. Let the sauce come to a boil and remove it from the stove, seasoning with salt and black pepper. Place the duck breasts in a greased baking tray and pour the sauce over them. Cover with foil and put the duck with oranges to bake in a preheated oven for a little more than an hour. Remove the meat and strain the liquid from the orange peels, put it on the stove together with 1 cup of orange juice and, once it boils, thicken it with the dissolved cornstarch. Once the sauce has thickened a little, season with spices. Serve a portion of duck, drizzled with sauce and sprinkled with crushed almonds. Garnish with round orange slices.