Grate the ½ medium English cucumber grated and squeezed dry on the large holes of a grater. Gather the grated medium English cucumber grated and squeezed dry in a clean kitchen shears towel or cheesecloth and squeeze out as much liquid as possible — this is key to a thick tzatziki, not a watery one.

In a mixing bowl, combine the 1 cup plain Greek yogurt full-fat, squeezed ½ medium English cucumber grated and squeezed dry, minced cloves garlic peeled, 1 tbsp extra-virgin olive oil, 1 tbsp fresh lemon juice, 1 tbsp fresh dill finely chopped, and 1 ½ tsp kosher salt. Stir well, taste, and adjust seasoning. Cover and refrigerate for at least 20 minutes (or up to 2 days) to let the flavors meld.

Pull the brisket from the refrigerator 30 to 60 minutes before cooking to let it approach room temperature. Trim hard fat down to about a quarter inch. Apply your dry rub or salt-and-pepper blend evenly over the whole surface, pressing it in firmly. Soak wood chips in water for at least 30 minutes if your smoker uses chips, or prep wood chunks and pellets per your smoker's directions. Empty the drip tray before you start. Set aside unwaxed butcher paper or heavy-duty aluminum foil for wrapping later in the cook.

Preheat your smoker to 225–250°F and verify the temperature with a standalone meat thermometer. Add wood chips, chunks, or pellets per your smoker's instructions. Place the brisket fat side up with the point end toward the heat source. Close the smoker and avoid opening it often. Check wood and adjust vents every 45 minutes to hold 225–250°F. Rotate the brisket every 3 hours and flip if one side colors faster. Smoke uncovered until the internal temperature hits 165°F and a dark bark has formed, about 5 to 8 hours. Wrap tightly in butcher paper or aluminum foil, return to the smoker, and continue until an instant-read thermometer reads 195–203°F and the meat is very tender but not falling apart, roughly 4 to 5 more hours. Total cook time is typically 8 to 12 hours. Use internal temperature and texture as your doneness cues, not the clock alone.

Warm the 6 whole pita bread directly over a gas flame for 30 seconds per side, in a dry skillet over medium heat, or wrapped in a damp paper towel in the microwave for 20 seconds.

To assemble each gyro: spread a generous spoonful of tzatziki down the center of a warm 6 whole pita bread. Layer on a handful of gyro meat slices, then top with sliced medium Roma tomatoes thinly sliced, ½ medium red onion thinly sliced, ½ medium English cucumber grated and squeezed dry, and crumbled 3 oz feta cheese crumbled if using. Fold the 6 whole pita bread around the filling and serve immediately.

Remove the loaf from the loaf pan and place it on a cutting board. Place another cutting board or heavy pan on top and weigh it down for 5–10 minutes — this compresses the loaf for cleaner, thinner slices (mimicking the density of spit-roasted gyro meat).

Switch your oven to broil on high. Slice the pressed loaf into thin strips, about ¼-inch thick. Spread the slices in a single layer on a aluminum foil-lined baking sheet. Broil 4–5 inches from the heat for 2–3 minutes, until the edges are browned and slightly crispy. Watch closely — they can go from golden to burnt quickly.

Warm the pita bread directly over a gas flame for 30 seconds per side, in a dry skillet over medium heat, or wrapped in a damp paper towel in the microwave for 20 seconds.

To assemble each gyro: spread a generous spoonful of tzatziki down the center of a warm pita bread. Layer on a handful of gyro meat slices, then top with sliced roma tomatoes, red onion, cucumber, and crumbled feta cheese if using. Fold the pita bread around the filling and serve immediately.