Set oven to 350°F (175°C).
Melt vegan butter directly in a 9×13-inch glass baking dish.
Whisk flax egg, milk, flour, sugar, baking powder, and salt until smooth.
Pour the batter over melted butter without stirring.
Spread pineapple chunks evenly and drizzle reserved juice.
Drop cubes evenly over pineapple layer.
Bake 45 minutes until golden, puffed, and bubbling.
Let cool 10 minutes before serving warm with vegan ice cream.
