CHUCK ROAST PREP: Pat roast all over with paper towel to dry. No need to remove any fat from the roast. Generously season on all sides with salt and pepper (I use 2 teaspoons fine sea salt and 1 and 1/2 teaspoons pepper for a 2.5-pound roast.). Spray a 6-quart slow cooker with nonstick spray.
SLOW COOKER: While searing the roast (see next step), add everything to the prepared slow cooker: 2 tablespoons Herbs de Provence, 1 tablespoon ground cumin, 1/2 tablespoon dried oregano, 1/2 tablespoon dried parsley, 1/2 tablespoon beef bouillon powder, tomato paste, crushed tomatoes, 1 tablespoon Worcestershire sauce, and 1/3 cup sun-dried tomatoes (use a fork to pull them from the jar and measure). Stir everything together in the slow cooker and press into one even layer before adding in the roast.
SEAR ROAST: Warm 2 tablespoons of the oil surrounding the sun-dried tomatoes (or regular olive oil) in a large Dutch oven (or oven-safe heavy-bottomed skillet/pot) over medium-high heat. Once you can feel the heat when you hold your hand 6 inches above the pot, place the seasoned chuck roast in the pan. Brown the beef about 4-5 minutes per side. (To get a good sear, let the beef cook without being turned; it will release easily once it's seared). Don't skip this step--we are adding layers of flavor here. Once the roast is nicely seared with a good crust, remove it from the skillet and place it in your slow cooker on top of the tomato and seasoning mixture (if there is a fat cap, place the cap facing up so fat can drip down and flavor the roast). Add in the bay leaf.
ONIONS AND GARLIC: Allow the skillet used for the beef to cool for about 5 minutes after removing the beef from it. Then return it to medium high heat and add another 2 tablespoons of the oil surrounding the tomatoes (or regular olive oil). Add in the diced onion and minced garlic. Stir and cook until tender, scraping up any bits left from the meat off the bottom of the pan, about 5 minutes. Pour this mixture, scraping every bit from the pan, over the roast in the slow cooker. Gently spoon the cooking liquid over the beef. Cover, and cook on low for 7-9 hours (8 hours is perfect in my slow cooker). Once the beef is cooked through (and shreds easily), remove the beef to a plate. Scrape off any fat cap if there is one and use two forks to shred the beef and then return it to the slow cooker. Stir the liquid left in the slow cooker. Return the shredded beef into the sauce in the slow cooker and gently stir. Turn the slow cooker to warm. Season beef to taste with salt and pepper. Add freshly squeezed lemon if desired-- we like 1-3 tablespoons (taste and add to personal preference).
TZATZIKI: I like to prepare this sauce when starting the beef so it has a chance to get more flavorful before serving! Grate a cucumber with the large holes of a cheese grater. Line a small bowl with a few paper towels (or a clean kitchen towel) and place the grated cucumber on top. Squeeze out as much extra moisture as you can from the cucumber (to keep the sauce from being watery). Once it's drained, add to a medium-sized bowl. Add in the 1/2 cup Greek yogurt, 1 teaspoon minced garlic, 1 and 1/2 teaspoon red wine vinegar, 1/2 teaspoon lemon zest, 1 tablespoon lemon juice, 1 and 1/2 tablespoons olive oil, and salt and pepper to taste (I add 1/4 teaspoon salt and 1/8 teaspoon pepper). Cover the bowl and place in the fridge until ready to serve.
SALAD: In a medium-sized bowl, combine the cucumbers, tomatoes, parsley, and red onion. In a small bowl, stir together the lemon juice, oil, paprika, and salt and pepper to taste (I add 1/4 teaspoon salt and 1/8 teaspoon pepper). Whisk with a fork. Drizzle dressing over vegetables and stir to coat.
CHAR PITA BREAD: Spray both sides of the pita bread with olive oil cooking spray and "grill" the bread on the stovetop over an open flame (on medium heat) until slightly charred, about 10-15 seconds per side (flip with tongs). Immediately fold in half after being charred and cover with a clean towel until ready to serve. Alternatively, warm (covered with a damp paper towel) in the microwave.
ASSEMBLY: Set everything out: grilled/warmed pita, sauce, and veggies. Use tongs to grab meat from the slow cooker and top the charred/warmed pita bread with. Top with veggies and drizzle tzatziki sauce on top. Enjoy immediately, garnished with additional parsley if desired. Serve with lemon wedges and drizzle lemon on before enjoying!