Cut 3 (½-inch-thick) slices from the tomato. Save the rest of the tomato to enjoy later.
Place a bowl or mold that is bigger than the circumference of the tomato slices (about 6 inches round) on the pie crusts, and carve out 3 circles. Save the scraps to enjoy later.
Lay the pie rounds flat on a parchment-lined baking sheet. Preheat the oven to 375°F (190°C).
Spread 2 tablespoons cream cheese over each pie round. Top each with 1 cheese slice and 1 tomato slice. Gently crimp and fold the edges of each pie crust to cover the sides of the tomato.
Whisk together the egg and water in a small bowl. Using a pastry brush or fork, brush the mixture over each crust. Sprinkle each galette with 1 tablespoon everything bagel seasoning.
Bake on a parchment-lined baking sheet for 15–20 minutes, until fully crispy and browned.
