Professional Baker Teaches You How to Make Upside Down Onion Cake

Ingredients

• 90 g Unsalted Butter (Melted for batter; extra 1 tbsp for skillet)
• 1.5 cups All-Purpose Flour (Sifted)
• 0.75 cups Parmesan Cheese (Finely grated, fresh)
• 3 tablespoons Cornstarch (Helps keep cake tender)
• 1 tablespoon Granulated Sugar (Just a hint of sweetness)
• 2 teaspoons Baking Powder (Leavening agent)
• 0.5 teaspoons Salt (Enhances flavor)
• 2 teaspoons Herb de Provence (Dried blend of thyme, rosemary, bay leaf, etc.)
• 6 tablespoons Sour Cream (Room temperature)
• 6 tablespoons Milk (Whole milk)
• 2 Eggs (Large, room temperature)
• 1 tablespoon Olive Oil (Prevents butter from burning; can use vegetable oil)
• 2 Onions (Regular cooking onions, sliced ½ inch thick, keep rings intact)

Instructions

1. Melt Butter for Batter

   Measure 90 g (6 Tbsp) unsalted butter and melt it gently in a small pot over low heat.

   Time: PT5M

2. Slice Onions

   Peel the onions and slice them about ½ inch (6 mm) thick, keeping the rings together.

   Time: PT5M

3. Combine Dry Ingredients

   In a mixing bowl combine 1½ cups flour, ¾ cup grated Parmesan, 3 Tbsp cornstarch, 1 Tbsp sugar, 2 tsp baking powder, ½ tsp salt, and 2 tsp herb de Provence. Whisk until evenly mixed and the cheese is broken up.

   Time: PT5M

4. Prepare Wet Ingredients

   In a separate bowl measure 6 Tbsp sour cream and 6 Tbsp milk, then whisk in 2 large eggs until just combined.

   Time: PT5M

5. Make the Batter

   Add the wet mixture to the dry ingredients, stir with a spatula just until combined, then fold in the melted butter.

   Time: PT5M

6. Caramelize Onions

   Heat the cast‑iron skillet over medium‑high, melt 1 Tbsp butter and add 1 Tbsp olive oil. When butter bubbles, add the onion slices, packing them without overlapping. Cook about 4 minutes until the edges soften and begin to caramelize.

   Time: PT4M

7. Add Batter Over Onions

   Remove the skillet from heat. Spoon the batter over the onions, spreading it evenly with a spatula to cover the entire surface.

   Time: PT2M

8. Bake the Cake

   Place the skillet in a preheated 400°F oven and bake for 25 minutes, or until a skewer inserted in the center comes out clean.

   Time: PT25M

   Temperature: 400°F

9. Cool Before Flipping

   Remove the skillet from the oven and let the cake cool in the pan for about 20 minutes to set and make flipping easier.

   Time: PT20M

10. Invert and Serve

    Run a thin spatula around the sides, place a plate over the skillet, and carefully flip the cake onto the plate. Slice into wedges and serve warm or at room temperature.

    Time: PT5M

Nutrition Facts

Calories

250

Protein

10 g

Carbohydrates

20 g

Fat

12 g

Fiber

1 g

Ingredient Substitutions

• Instead of Unsalted Butter: Margarine
• Instead of All-Purpose Flour: Whole wheat flour (will be denser)
• Instead of Parmesan Cheese: Pecorino Romano
• Instead of Cornstarch: All‑purpose flour (less effective)
• Instead of Granulated Sugar: Honey (reduce liquid)
• Instead of Baking Powder: Baking soda + cream of tartar
• Instead of Salt: Sea salt
• Instead of Herb de Provence: 2 teaspoons dried oregano
• Instead of Sour Cream: Greek yogurt
• Instead of Milk: Half‑and‑half
• Instead of Eggs: Egg replacer (1/4 cup each)
• Instead of Olive Oil: Canola oil
• Instead of Onions: Sweet onions

Equipment Needed

• Heavy Cast Iron Skillet
• Mixing Bowl
• Whisk
• Spatula
• Measuring Cups
• Measuring Spoons
• Chef's Knife
• Cutting Board
• Skewer or Toothpick
• Plate for Flipping
• Oven Mitts

Critical Steps — Do Not Skip

• Melt butter without browning
• Caramelize onions without burning
• Do not overmix the batter
• Bake until a skewer comes out clean
• Cool the cake before flipping

Chef Tips from the Video

• Use freshly grated Parmesan for maximum flavor and texture.
• A cast‑iron skillet provides even heat and a beautiful crust.
• Room‑temperature eggs and dairy blend more smoothly into the batter.

Troubleshooting

Storage

Refrigerator: Store in an airtight container for 3–4 days.

Freezer: Wrap tightly and freeze up to 2 months; reheat in oven.

Room temperature: Can sit at room temperature for up to 2 hours.

Make-Ahead Tips

• Caramelize the onions up to a day ahead and refrigerate.
• Prepare the batter and keep it chilled; give it a quick stir before baking.
• Bake the cake a day ahead, cool completely, then reheat slices in a 350°F oven for 10 minutes.

Frequently Asked Questions