Spray a large mixing bowl and a 9x13-inch baking pan lightly with nonstick spray. Set aside.
Combine the buttermilk and butter in a microwave-safe bowl. Cover and microwave in 20-second increments until the mixture is warmed to about 115°F.
½ cup buttermilk, 4 tablespoons unsalted butter
In the bowl of a stand mixer fitted with the paddle attachment, whisk the buttermilk mixture and yeast together. Allow to rest for 10 minutes.
2¼ teaspoons instant yeast
Add the pineapple juice, brown sugar, salt, vanilla, and eggs. stirring on low until combined.
½ cup pineapple juice, ⅓ cup brown sugar, 1 teaspoon kosher salt, 1 teaspoon pure vanilla extract, 2 large eggs, 1 large egg yolk
Gradually add in 2 cups of flour and mix on medium speed for 1 minute. Continue adding the rest of the flour on low speed until a soft dough forms. Add more flour if necessary.
4½-5 cups all-purpose flour
Replace the paddle attachment with a dough hook and knead on medium speed for 5-6 minutes until the dough forms a soft, smooth ball. Alternately, you can do this by hand for 8-10 minutes.
Place the dough into the prepared bowl and cover with plastic wrap or a clean towel. Place in a warm spot in your kitchen and allow to rise for 1 hour*, until doubled.
Remove the dough from the bowl and divide it into 15 equal pieces. Round the dough into balls and place them in the prepared pan. Cover and rest for 30 minutes*, until doubled.
Preheat the oven to 375°F.
Whisk together the reserved egg white and 1 teaspoon water. Lightly brush the tops of the rolls with the egg wash. Bake for 20-25 minutes, until golden brown.
1 teaspoon water