Heat oven to 350°F

Line bread pan with parchment paper - use one sheet to cover the long sides and bottom, fold against the short sides of the pan

Rice cauliflower in food processor - even if you buy pre-riced you'll want to make it as fine as possible

Steam cauliflower in mircrowave until it is soft - you can also gently steam in a pot or pan on the stove, just make sure it doesn't start to brown

Allow cauliflower to cool a bit

While cauliflower is cooling, separate eggs

Place the whites into a mixing bowl or stand mixer bowl and set the yolds aside

Beat egg whites until stiff peaks form

Set beaten egg whites aside

When cauliflower is cool enough, place in a clean dish towel or mesh bag and squeeze out as much water as you can - there should be a fairly dry ball of the cooked cauliflower and it will be reduced in size by about half - 1 ½ cups or so left. Set strained cauliflower aside,

Add the egg yolks, almond flour, melted butter, olive oil, baking soda, apple cider vinegar and salt to large mixing bowl or stand mixer bowl

Beat for a beat at medium speed until everything is combined

Add the cauliflower

Beat at medium speed until the cauliflower is thoroughly mixed in

Carefully fold in a third of the whipped egg whites using a spatula. You want the batter to remain airy. Contiue adding the rest of the egg white, gently folding in until they are mixed with the batter. Don't stir them in, just incorporate so they are mixed with the batter, but still airy

Pour batter into parchment-paper-lined bread pan

Bake for 50 - 55 minutes until bread is firm on top in the middle of the loaf

Cool in pan on wire rack for 15 - 20 minutes

Lift loaf out the pan using the parchement paper and place the loaf on the wire rack

Cool completely before slicing

To store: Wrap loaf in paper towel and place in an air-tight bag or container. Store in refrigetor for up to a week. Freeze bread for up to three months - freezing tip - slice bread and place pieces of parchment paper between each slice before freezing.