Preheat oven to 400'F and prepare water bath. You will need a 9 x 12 inch baking dish and a pot of boiling water. 

Generously butter the ramekins and then sprinkle them with sugar. Dump the excess sugar out. Put in refrigerator until ready to use.

Zest and juice the 4 oranges. Strain the juice through a fine mesh sieve or colander...you should have about 1 cup.

Boil juice and butter in a pot over medium high heat, until reduced by one-quarter. 

Reduce heat to low and add orange zest and flour and stir until it forms a paste.

Add sugar, 1/4 teaspoon salt and vanilla and cook until the mixture is gelled. 

Remove from heat and whisk in egg yolks until the mixture becomes creamy.

Put egg whites, pinch of salt and cream of tartar in the bowl of electric mixer with whisk attachment. Beat on low for 1 minute, medium for 1 minute and then high speed until glossy and medium-firm peaks form.

Gently fold egg whites into orange mixture, being careful not to over mix. Incorporate the whites into the base by pushing lightly down while bringing the heavier orange mixture up and over the whites. Use a sweeping S motion.

Fill buttered and sugared ramekins with mixture. 

Place the ramekins in the baking dish and then fill the baking dish with water so that the water comes halfway up the sides of the ramekins. 

Bake for 10 minutes at 400'F and then reduce the heat to 350'F and bake for 15 additional minutes until puffed and golden brown.

Don't open the oven door until souffles are fully baked.

Dust with powdered sugar and serve immediately.