In a plastic bag, place the flour and some salt, shake it to mix it together then add the sole to the bag and shake it to lightly dust the sole all over. In a very large frying pan, big enough to hold all the soles some olive oil, fry gently on both sides till golden, about 3 minutes per side, depending on the size of the soles.
Add some black pepper to the sole when you turn it over. Keep the soles warm while you deglaze the pan. Place half the butter into the same frying pan and add the thyme and capers, allow the butter melt a bit and then add the zest and juice of one lemon.
Put the sole back into the pan with the remaining butter and fresh parsley. Once the butter has melted, serve it with your favourite green vegetables.