A mild white fish like cod practically begs to be dressed in big, bold flavors, which this lemon-chile sauce definitely delivers. Sizzling chickpeas, garlic, and whole lemon slices in olive oil with Aleppo-style pepper and smoked paprika creates a puckery, smoky, earthy base; adding a pat of butter and a slow stream of water builds it into an emulsified sauce. Start with about ⅓ cup water and keep adding as needed, stirring the mixture to combine, until you reach a drizzly consistency that will spill over the fish and pool on your plate.