Overheating can cause the curd to become grainy or scrambled or lumpy. Fixing lumpy lemon curd involves smoothing out the texture to achieve a creamy consistency. Here are some ways that you can do this: Straining: Get a fine mesh sieve or strainer and place it over a clean bowl. Pour the lumpy lemon curd through the strainer. The mesh will catch the lumps while allowing the smooth lemon curd to pass through. Use a spatula or the back of a spoon to press the curd through the sieve. Blend or Use an Immersion Blender: If straining doesn't fully fix the lumpiness, use a regular blender or an immersion blender. Transfer the curd to a blender, or use the immersion blender directly in the saucepan, and blend it on a low setting until smooth.