Preheat your oven to 350°F (175°C). Grease a 9x5 inch loaf pan and line it with parchment paper.
Make the cookie crumble topping by combining the 1/2 cup gluten free flour, 1/4 cup brown sugar, and a pinch of salt in a small bowl. Add the cold cubed butter and use your fingers to pinch and rub the mixture together until you get coarse, pea-sized crumbs. Refrigerate while you make the batter.
In a medium bowl, whisk together the 2 cups gluten free flour, almond flour, baking powder, baking soda, and salt.
In a large bowl, beat the softened butter and dark brown sugar with an electric mixer until fluffy, about 3 minutes. Beat in the eggs one at a time, then mix in the vanilla extract, sour cream, and 1/3 cup salted caramel sauce until smooth.
Fold the dry ingredients into the wet ingredients using a spatula until just combined. Pour the batter into the prepared pan and smooth the top.
Drizzle a couple of tablespoons of extra salted caramel sauce over the top of the batter in a zigzag pattern. Scatter the chilled cookie crumble topping evenly over the surface, then sprinkle with flaky sea salt.
Bake for 55 to 65 minutes, tenting loosely with foil at the 40-minute mark if the crumble is browning too fast. The bread is done when a toothpick inserted into the center comes out mostly clean. Let it cool in the pan for 15 minutes, then transfer to a wire rack.