Preheat the oven to 350°F. Grease a 9x13-inch baking dish with nonstick cooking spray or butter.
Cut the Texas toast into 1-inch cubes and arrange evenly in the prepared baking dish.
In a large bowl, whisk together the eggs, pumpkin puree, Lifeway Kefir, granulated sugar, cinnamon, vanilla, cloves, nutmeg, and salt until smooth and well combined.
Pour the pumpkin custard evenly over the bread cubes. Gently toss to coat, then lightly press the bread down into the custard.
Let the casserole sit for 10–15 minutes to allow the bread to absorb the pumpkin custard.
Meanwhile, add the brown sugar, flour, cinnamon, and softened butter to a small bowl. Mix with a fork until a crumbly mixture forms.
Sprinkle the brown sugar crumble evenly over the casserole.
Bake uncovered for 40–50 minutes, or until the center is set and the top is golden brown. If the crumble starts to brown too quickly, loosely cover the casserole with aluminum foil.
Remove from the oven and let rest for 5–10 minutes before serving.
Serve warm with maple syrup and powdered sugar, if desired.