In a small saucepan, whisk together the sugar, flour, egg, water, and lemon juice. Cook over medium heat, stirring often, until the mixture thickens—about 3 to 5 minutes.

Remove the pan from heat. Stir in the lemon zest, butter, and vanilla extract until smooth. Set aside to cool, then place in the fridge to chill for 30 minutes.

While the glaze chills, wash and slice the fruit. Add grapes, raspberries, sliced bananas, and apples to a large mixing bowl. Add any optional fruits as desired.

Once the glaze is chilled, pour it over the prepared fruit. Gently toss until all the fruit is evenly coated.

Serve immediately or refrigerate until ready to serve. Best enjoyed within a few hours of making.