Place strawberries in a high-performance blender (such as a Vitamix®) and process on low variable 1, quickly increasing to 10 and blend for about 20 seconds. Press mixture through a fine-mesh sieve over a bowl, and discard the seeds.

Melt butter in a saucepan over medium heat. Pour in strained strawberry puree. Add sugar and vanilla extract and whisk together thoroughly. Allow mixture to come to a boil and bubble until slightly thickened, about 6 minutes.