• The recipe is for 7-inch (18 cm) chiffon tube pan

Prepare the Red Date Puree:

• Soak the red dates in warm water until soft (about 15–20 minutes)
  
• Drain and squeeze out excess water. Blend with 50 grams of milk into a coarse puree. Set aside
  

Make the Yolk Batter:

• If you choose to do slit-top version: start preheating the oven at 385 F (195 C) for conventional oven. For convection oven,lower the temperature by 20 F (15 C). Position the rack to the lower 3rd of the oven
• If you choose to do regular bake without the slit: start preheating the oven at 330 F (165 C) for conventional oven. For convection oven,lower the temperature by 20 F (15 C). Position the rack to the lower 3rd of the oven
• In a mixing bowl, combine the red date puree, oil, milk, and egg yolks.
  
• Whisk the mixture until it emulsifies (combines well and the oil doesn't separate from the mixture). Sift in the cake flour and salt. Mix until just combined—don’t overmix.
  
• Fold in the finely chopped toasted walnuts.
  

Make the Meringue:

• In a clean, grease-free bowl, beat the egg whites with lemon juice until foamy. Gradually add the brown sugar in 3 additions
  
• I beat them at medium speed (speed 4 on Kitchen Aid). This will take a bit longer than beating at high speed. I used to do higher speed (speed 6 or even 8), but the meringue is smoother and nicer when I maintain the speed on 4 and much more stable too.
• I highly recommend stopping several times to check on the consistency and scraping the sides of the bowl to make sure no sugar left on the side of the bowl. Whip until you reach a stiff peak but still have a slight bent on the tip. Then lower the speed to 2 and whip for 1 minute to even out large bubbles and stop beating
  

Combine:

• Gently fold in 1/3 of the meringue into the thick batter. Using a rubber spatula, swipe from the side and gently fold over to mix and then continue. Repeat this motion several rounds. Since the batter is a bit thicker, it's okay to take a bit more time to make sure the meringue and the batter really combined. You shouldn't see any streaks of egg white meringue. You can be a bit more "rough" for this first round.
  
• Continue on with the second 1/3  of the meringue again to mix. You want to be gentler now but make sure the two are well-combined.
  
• Continue with the last 1/3 and the batter should be well-combine and you shouldn't see any streaks of white meringue and the batter has really good volume and airy
  
• Pour the batter into an ungreased 7-inch chiffon tube pan.
  
• Use a skewer to go round and round to even out the batter and to pop up any large bubbles along the way while doing that
  
• Tap the pan on the counter a few times to release big air bubbles.
  

Bake (If you choose to do the slit-top version):

• Bake at 385 F (195 C) for 13–14 minutes, then quickly remove the cake from the oven and slit the top lengthwise, about 1/2-inch deep, with a sharp knife (this helps it rise evenly following the slit lines). Wipe the knife after each slit. Try to complete this in less than 1 minute.
  
• Return to the oven, reduce the heat to 330 F (165C), and bake for another 50 minutes or until the top is dry to the touch and springs back slightly when pressed. For convection oven,lower the temperature by 20 F (15 C)
  

Bake (without the slit-top):

• Pop into the oven and let it bake at 330 F (165 C) for 55-60 minutes or until the toothpick inserted into the middle of the cake comes out clean. The top shouldn't be wet and bounce back when you gently press on it with your finger.

Cool:

• Immediately invert the pan upside down and cool completely before unmolding.

Unmolding:

• Run a thin knife around the edges and the center of the tube to release the cake. Then run a knife underneath the base. Carefully unmold the chiffon cake. For the slit-top chiffon cake, the cake can be placed upside down like usual, or with the slit top on top