In a large bowl, whisk together flour and salt. Add oil, then flour mixture, to yeast mixture. Mix on low speed for 4 minutes or until dough forms a coarse ball and clears sides and bottom of bowl (add more flour or water by the tablespoonful, if needed). Let dough rest, uncovered, 15 minutes, then knead on medium-low speed 2 minutes more, or until dough is smooth and tacky, but not sticky. If dough is too soft and sticky to hold its shape, mix in more flour by the tablespoonful. If it is too stiff or dry, mix in more water by the tablespoonful. (If not using a mixer, dough can be combined in a large bowl and, on a lightly floured work surface, vigorously kneaded by hand, following kneading and resting times above.) Form dough into a ball and place in a bowl lightly brushed with oil; roll dough in oil to coat. Cover bowl tightly with plastic wrap. Let stand at room temperature 2 hours or until dough is doubled in bulk.

 

FOR TOPPING: During second hour of dough rise, heat oven to 375º with rack in middle. Meanwhile, in a large nonstick skillet, heat oil over medium-high heat. Add potatoes, placing them in single layer; reduce heat to medium-low and cook, turning once and lightly seasoning both sides with salt as you go, until just tender, about 10 minutes total (do not brown). Leaving oil in skillet, transfer cooked potato slices to a plate in a single layer to cool. Return skillet to medium-low heat; add onion and generous pinch salt; cook, stirring occasionally, until onion is tender, about 10 minutes. Remove from heat. 

 

ASSEMBLE PIZZA: Generously grease 9-inch round nonstick springform pan with oil. Shape and press dough into pan, pressing with fingertips to stretch dough to edges. Let rest 5 minutes. 

 

Arrange tomatoes over dough, leaving a 1/2-inch border. Sprinkle with oregano, then top with potato slices, overlapping slightly, and onion. Bake until crust is lightly golden and edges are pulled away from sides of pan, about 40 minutes. 

 

Run a butter knife along edges of pizza, then cool 5 minutes in pan on wire rack. Release from pan and transfer to a cutting board. Top with porchetta and cheese. Serve hot.