Guava fruit paste is a vibrant, sweet Mexican confection with tropical aroma. This family-friendly treat is a firm, fruity candy that pairs beautifully with fresh cheese.
Wash and roughly chop the guavas, leaving the skin on but removing the ends and any seeds.
Add guavas and water to a medium saucepan; cook over medium heat until the fruit softens and breaks down, about 20 minutes. Stir occasionally.
Press the softened guava mixture through a fine mesh sieve or food mill to obtain a smooth purée. Discard the seeds and skins.
Return the guava purée to the cleaned saucepan. Stir in the sugar and lemon juice. Cook over low heat, stirring frequently to prevent sticking.
Simmer until the mixture thickens significantly, pulls away from the pan, and a spoon dragged across the bottom reveals the pan, 40-60 minutes. Lower the heat if mixture bubbles too rapidly.
Pour the thick paste into a parchment-lined loaf pan or similar mold. Level the top, let cool to room temperature, then chill until firm (at least 1 hour). Slice and serve.