Preheat the oven to 400°F (200°C, or gas mark 6). Line a large baking sheet (13 x 18 inches [33 x 46 cm] or larger) with parchment paper.

In a high-speed blender, combine the cashews, water, nutritional yeast, lemon juice, garlic, onion powder, and salt. Blend until creamy and smooth, 1 to 2 minutes. Transfer to a bowl, and stir in the cheese and spinach. Set aside.

Take the parchment from the baking sheet and lay it on a flat surface. Roll out the pizza dough to a 10 x 12-inch (26 x 30-cm) rectangle on the parchment paper. With a pizza cutter or sharp knife, cut the dough into the shape of a tree with the tip at the top; keep the excess dough where it lays—don’t gather it or remove it from the parchment. Carefully transfer the parchment paper with the dough on it back to the baking sheet. Spread the spinach mixture over the tree part of the dough, leaving a ½-inch (1-cm) border all around the tree dough. Flip the 2 pieces of dough that were cut off from the sides, so that the bottom points are now up top, and lay the pieces over the filling to match the shape of the tree and cover the filling. Pinch the 2 pieces of the top layer of dough together in the middle and pinch all sides of the dough together to close in the filling. Cut 7 lines, through to the bottom, from either side of the dough toward the middle of the tree, being careful to leave the dough connected in the middle; there will be 8 “tree branches” on each side. Twist each branch toward the bottom one time. Bake for 20 to 22 minutes, or until crispy and golden brown. While it’s baking, mix together the butter, garlic powder, and Italian seasoning.

When the bread is done, remove from the oven and immediately brush with the butter mixture. Sprinkle with coarse salt, if desired. Serve warm with the marinara.