Add shallots, garlic, peppercorns, parsley, and bay leaf to a large skillet. Add lemon juice and lemon, white wine, and enough water to come about 2 inches up the pan.
Bring the skillet to a simmer over medium-high heat.
Turn heat down to low. Add sole filets and let them poach in the liquid for about 4 minutes per side.
In a small bowl, combine butter, lemon juice, and capers and microwave for 2 minutes on low.
Transfer fish using a spatula straight to plate from the poaching liquid. Serve fish with a carb of your choosing and the caper butter sauce.