Season the meat with salt and pepper, add oregano, brush it with mustard and place it in the casserole dish.
Cut the vegetables into thick slices and place them on top of the pieces of meat.
Add the water, pour a little olive oil, cover with the lid and bake in a strong oven (220°C) for 2 hours.
Then mix the orange juice, lemon juice and 1 tbsp mustard, pour it over the meat and continue baking without the lid at 180°C until the meat absorbs most of its juices and it is left with just a little sauce.
Attention! During the second phase of baking turn the pieces of meat over every half hour.