Preheat your oven to 350° F. Spray an 8x8 inch baking pan with nonstick baking spray. Set aside.
Remove butter from fridge to soften.
Make the prune filling: in a food processor, process 8 oz. of California Prunes (chop them into smaller pieces if needed) with ¼ cup lemon juice, cinnamon, brown sugar and vanilla extract. Process for 1-2 minutes or until prunes are blended well into a paste.
Make the oatmeal crumb mixture next: In a medium sized bowl, combine the dry ingredients: oats, flour, sugar, baking soda and salt.
With clean hands, mix softened butter into the dry ingredients until the mixture becomes crumbly. Press half of the oatmeal mixture down into the pan to crease the crust layer.
Evenly spread the prune mixture on top.
Then sprinkle the remaining crumb mixture on top and press lightly into the prune paste.
Bake for 35 minutes or until the top is golden brown. Let cool completely and then cut into squares.