Preheat oven to 350°F (175°C). Line a baking sheet with parchment paper or lightly grease with cooking spray.
In a bowl, cream 1/2 cup softened butter and 1 cup granulated sugar until light and fluffy.
Beat in 1 egg and 1 tsp vanilla extract until well combined.
In a separate bowl, whisk 2 cups flour, 1/2 tsp baking soda, and 1/4 tsp salt.
Gradually add dry ingredients to the wet mixture. Mix until just combined.
Gently fold in 1 cup diced rhubarb (and 1/2 cup chopped nuts if using).
Drop spoonfuls of dough onto the baking sheet, spacing them apart.
Bake in preheated oven for 12-15 minutes, until edges are golden brown.
Allow cookies to cool on a baking sheet for a few minutes, then transfer them to a wire rack to cool completely.
Serve and enjoy these delightful Rhubarb Cookies!