Make the Dough: Whisk together the flour, cornmeal, salt, sugar, and yeast in a large bowl.
Add water and melted butter and mix on low speed, using a dough hook, until fully combined, 1 to 2 minutes, scraping sides and bottom of bowl occasionally. Increase speed to medium and knead until the dough is glossy and smooth and pulls away from sides of the bowl, 4 to 5 minutes. (You can easily make this by hand, mixing in the water and butter with a spatula and then kneading by hand.)
Coat a large bowl with 1 teaspoon olive oil. Using a greased spatula, transfer the dough to the bowl, turning to coat the dough in oil; cover tightly with plastic wrap. Let rise at room temperature until nearly doubled in volume, 45 to 60 minutes.
Make the Sauce: While dough rises, heat the butter in a medium saucepan over medium heat until melted. Add onion, oregano, and salt; cook, stirring occasionally until liquid has evaporated and onion is golden brown, about 5 minutes. Add garlic and cook until fragrant, about 30 seconds.
Stir in tomatoes and sugar, increase heat to high, and bring to a simmer. Lower heat to medium-low and simmer until reduced to about 2½ cups, 25 to 30 minutes. Off the heat, stir in the basil and olive oil, then season with salt and pepper.
Laminate the Dough: Turn the dough out onto dry work surface and roll into a 15×12-inch rectangle. Using an offset spatula, spread the softened butter over the surface of the dough, leaving a ½-inch border along the edges. Starting at the short end, roll the dough into a tight cylinder. With seam side down, flatten the cylinder into an 18×4-inch rectangle.
