Combine pears, sugars, and lemon juice in a large heavy-bottomed pot. Let sit for 15 minutes to draw out juices.
Bring to a boil over medium-high heat, stirring occasionally. Reduce heat to low and simmer, stirring frequently, until pears are very soft and mixture has thickened, about 45-60 minutes.
Remove from heat and stir in vanilla, cinnamon, nutmeg, and cloves.
Blend with an immersion blender or in a regular blender (in batches) until smooth.
Return to pot and simmer for another 5 minutes if too thin. Cool completely.
Transfer to sterilized jars and refrigerate for up to 3 weeks or freeze for longer storage.
Tips
For a smoother butter, peel the pears before cooking.
Store in airtight containers in the refrigerator for up to 3 weeks or freeze for up to 6 months.