Preheat your oven to 350°F and butter an 8x8-inch baking dish generously. Toss your 2 cups of bread cubes into the dish — you want them distributed evenly so every bite gets that custardy texture. Sprinkle the cinnamon and salt over the bread.

Whisk together the eggs, milk, 1/2 cup sugar, vanilla bean paste, and lemon zest in a bowl until completely combined. Don't skip the lemon zest — it brightens everything and makes the berry flavor pop even more. Pour this custard mixture right over the bread cubes.

Let the bread soak for about 5 minutes so it absorbs some of the custard mixture. Meanwhile, melt your butter in a small saucepan over medium-low heat. Gently fold the mixed berries into the bread and custard combination (be careful not to crush them too much).

Pour the melted butter evenly over the top and give it a gentle stir to incorporate. Bake for 40-45 minutes until the top is golden brown and a knife inserted in the center comes out clean. The edges will feel a little set, and the center should jiggle just slightly.

While the bread pudding bakes, make the vanilla sauce by whisking the heavy cream with 1/4 cup brown sugar in a saucepan. Heat over medium, stirring constantly until the sugar dissolves completely. The mixture should get all bubbly and thick — this takes about 8-10 minutes.

Whisk the cornstarch with 1 tbsp of cold water to create a slurry, then stir it into the warm sauce to thicken it up. Keep stirring for 2-3 minutes until it reaches that pourable consistency you want. Remove from heat and let it cool slightly.

Pull the summer berry bread pudding from the oven and let it rest for 5 minutes before serving. Spoon into individual bowls and drizzle generously with the vanilla sauce. The warmth is crucial here — this dessert tastes best served hot or warm.