Strawberry Rhubarb Curd

Combine rhubarb, strawberries, and lemon juice in a saucepan over medium heat. Cover and cook, stirring occasionally, until mixture begins to boil, about 5 minutes. Reduce heat to low and cook 2 more minutes. Remove from heat and cool slightly.

Pass mixture through a food mill, using the disc with the smallest holes. If you don't have a food mill, you can either puree the mixture with a food processor or immersion blender, or push it through a fine mesh strainer.

Fill the bottom of a double-boiler with about 1 inch of water and bring water to a simmer. Combine the eggs, egg yolk, and sugar in the top of the double-boiler and whisk together. Place over the bottom of the double-boiler and continue whisking until the sugar is dissolved.

Slowly whisk in the strawberry-rhubarb puree and continue whisking until the mixture is thick enough to coat the back of a metal spoon. Add butter and whisk until smooth.

Pour into a sterile jar, cool to room temperature, and refrigerate for up to 3 weeks.