Preheat your oven to 350°F (175°C). Grease and flour a standard 9x5 inch loaf pan, or line it with parchment paper leaving an overhang.

In a medium bowl, whisk together the 1 3/4 cups flour, baking soda, salt, and cinnamon. Set aside.

In a large bowl, cream together the softened butter and 1 cup granulated sugar until light and fluffy (about 3 minutes). Beat in the eggs one at a time, then stir in the vanilla extract.

Gradually mix the dry ingredients into the wet ingredients alternately with the milk, beginning and ending with the dry ingredients (mix just until combined; do not overmix).

Gently fold in the diced rhubarb and strawberries. Pour the batter into the prepared loaf pan.

Prepare the topping: In a small bowl, combine the 1/2 cup flour, 2 tablespoons reserved granulated sugar, and brown sugar. Cut in the cold cubed butter using a pastry blender or your fingers until coarse crumbs form. Sprinkle evenly over the batter.

Bake for 50–60 minutes, or until a toothpick inserted into the center comes out clean. If the topping browns too quickly, loosely cover the loaf with foil for the last 10 minutes of baking.

Let the bread cool in the pan for 15 minutes before gently removing it to a wire rack to cool completely before slicing.