Prepare the ingredients by washing and chopping the rhubarb into 1-inch pieces and hulled strawberries halved. Measure out the sugar, vanilla, and lemon juice.
Combine the chopped rhubarb, strawberries, sugar, vanilla extract, and lemon juice in the medium saucepan. Stir to evenly distribute the ingredients.
Place the saucepan over medium heat. Cook, stirring frequently with a wooden spoon or silicone spatula, until the mixture begins to bubble and the sugar dissolves completely.
Reduce the heat to low once bubbling occurs, and continue cooking for about 15-20 minutes. Stir occasionally and watch for the fruit to soften, releasing juices, and the mixture to thicken slightly with a glossy appearance.
Remove from heat when the fruit is tender, the mixture has thickened to a sauce-like consistency, and the colors are vibrant and deepened. Let it cool slightly before serving or storing.
Serve the compote warm or chilled over desserts, yogurt, or breakfast items. Optionally, spoon into jars for storage.