Preheat oven to 425 degrees F
Sift together the 1 cup sugar, 3 tablespoons flour, and salt together and set aside.
Combine the sour cream, eggs, and vanilla add to the dry ingredients and mix until smooth.
Add the strawberries and the rhubarb to the sour cream mixture and mix until well combined.
Pour in the prepared pie shell.
Place in the preheated oven and bake for 15 minutes. Turn the oven down to 350 degrees and continue to bake for 30 additional minutes.
While the pie is baking prepare the crumble topping. Mix the flour, sugar, and butter until well combined.
After the pie has baked the 45 minutes remove and sprinkle with the crumble topping. Place back in the oven and bake another 15 minutes.
Remove from the oven and set on a cooling rack to cool.