Combine raspberries, sugar, and lemon juice in a medium pot. Mix thoroughly.
Heat on high for 10 minutes, stirring frequently to prevent burning. Reduce heat to medium-low and simmer 8–10 minutes more, stirring constantly until juice evaporates.
Remove from heat. The mixture thickens as it cools to room temperature.
Once cooled sufficiently, transfer to a jar or container and refrigerate for up to 4–6 weeks.
Video
Notes
The recipe is adaptable — other seasonal fruits can be substituted for comparable results.