Preheat your oven to 375°F (190°C). This step ensures the cake bakes evenly from the start.
In a 13x9-inch baking dish, combine the strawberries, ¼ cup of granulated sugar, and ¼ teaspoon of kosher salt. Stir everything together until well mixed. The sugar will help release the juices from the strawberries as they bake.
Roast the strawberries for 30 to 40 minutes. Every 10 minutes, stir them gently to allow even roasting. You'll know they are done when they are soft, fragrant, and have released plenty of juices.
Reduce the oven temperature to 325°F (170°C). This lower temperature is perfect for baking the cake without burning the top.
Strain the roasted strawberries through a fine-mesh sieve into a medium bowl, reserving both the solids and liquids. Allow the berries to cool completely for about 15 to 20 minutes, then chop them into ¼-inch pieces.
In the bowl of a stand mixer fitted with the paddle attachment, beat the unsalted butter and the remaining 3¼ cups of granulated sugar on medium-high speed until the mixture is light and fluffy. This should take about 5 to 7 minutes. Be sure to scrape down the sides of the bowl and the paddle regularly.
Add the eggs one at a time, mixing well after each addition. This helps to incorporate air into the batter, making it light.
Mix in the vanilla extract until well combined.
In a separate bowl, whisk together the all-purpose flour, baking powder, and the remaining 2¼ teaspoons of kosher salt. With the mixer on low speed, gradually add this flour mixture alternately with the buttermilk, beginning and ending with the flour mixture. Stop mixing as soon as combined.
Gently fold in the chopped roasted strawberries with a spatula until everything is well incorporated.
Prepare an 18-cup tube pan by spraying it with baking spray that contains flour. Use a pastry brush to spread any excess spray evenly, blotting the brush as necessary. Spoon the batter into the prepared pan, smoothing the top with an offset spatula.
Tap the pan forcefully on a kitchen towel-lined counter several times. This helps to settle the batter and releases any air bubbles.
Bake for 1 hour and 25 minutes to 1 hour and 35 minutes, or until a wooden pick inserted near the center comes out clean. You can also check with an instant-read thermometer; it should register 205°F (96°C). Rotate the pan halfway through baking and loosely cover with foil if it gets too brown.
Allow the cake to cool in the pan on a wire rack for 15 minutes. Then, carefully remove it from the pan and let it cool completely, top side up, on the rack.
For the glaze, whisk together 3 to 4 tablespoons of the reserved roasted strawberry juice, the confectioners’ sugar, the melted unsalted butter, and the kosher salt in a small bowl until smooth. Spoon this glaze over the cooled cake.
Store the cake in an airtight container for up to 3 days, although it might not last that long with how delicious it is!
