Heat olive oil in a large pan over medium heat.
Sauté red onion until soft and translucent.
Add carrot, red pepper, cauliflower, and zucchini. Cook for 5–7 minutes until slightly tender.
Stir in green onions and season with salt. Remove from heat.
Step 3: Prepare the Batter
In a large bowl, whisk together eggs and milk until smooth.
Gradually mix in flour and baking powder to form a slightly thick batter.
Step 4: Combine Vegetables and Batter
Fold the sautéed vegetables into the egg and flour mixture until evenly coated.
Step 5: Bake
Pour the mixture into the prepared casserole dish.
Bake for 35–40 minutes, or until the top is golden and a toothpick inserted comes out clean.
Step 6: Serve
