DIAGNOSIS Odors are trapped in the silicone seal around the lid's removable center piece (the measured pour lid). That silicone is porous and absorbs smells.
FIX Pop out the clear plastic measured pour lid from the main lid. You'll see a thick silicone gasket around its edge. Remove that gasket. Wash the gasket, the pour lid, and the main lid separately in hot, soapy water. For the silicone gasket, the best trick is to soak it in a mixture of water and white vinegar (50/50) or a weak baking soda solution for a few hours. Rinse thoroughly and let all parts air-dry completely before reassembling.
IF THAT DIDN'T WORK For persistent smells, especially from oily ingredients like nut butters, the plastic itself might have absorbed odor. Try soaking the disassembled parts in a solution of warm water and a denture cleaning tablet overnight.
HEADS UP Avoid putting the silicone gasket or the plastic lid in the dishwasher's heated dry cycle if you can. The high heat can bake odors in and degrade the silicone faster. Hand washing is best for these parts.