Preheat oven to 425°F and line a rimmed sheet pan with parchment; toss broccoli florets with 1 tablespoon olive oil and a pinch of salt, spread in a single layer, and roast 10–12 minutes until edges brown lightly; cool 5 minutes.

Lower oven to 350°F and grease or line an 8×8-inch pan with parchment; transfer roasted broccoli to a food processor and pulse 6–8 times until small pieces form but not a puree.

In a large bowl whisk 3 large eggs, 1/2 cup Greek yogurt, 1 tablespoon lemon zest, and 1 teaspoon Dijon mustard until combined; stir in 1 cup crumbled feta and 1/3 cup grated Parmesan, then fold in pulsed broccoli.

In a separate bowl whisk 3/4 cup all-purpose flour, 1/4 cup almond meal, 1 teaspoon baking powder, 1/2 teaspoon kosher salt, and 1/4 teaspoon black pepper; fold dry ingredients into the broccoli-cheese mixture and add 1 tablespoon milk only if the batter seems too dry.

Spread batter evenly into the prepared 8×8 pan and smooth the top; bake at 350°F for 25–30 minutes until the top is lightly golden and a toothpick inserted comes out with a few moist crumbs; cool in the pan 10 minutes, then transfer to a wire rack and cool another 20–30 minutes before slicing into 12 bars.

Optional: for a crispier top, broil 1–2 minutes at the end of baking watching closely; store cooled bars in an airtight container in the refrigerator up to 4 days or freeze individually for up to 3 months.