I wanted to add a bit re chemical leaveners...
As mentioned, because your recipe is using only a small amount of flour, as well as almond paste and eggs, then I'm assuming the eggs are giving the majority of the volume and stability (the paste is probably weighing the batter down a bit). There are different types of chemical leaveners, and each effect cakes in very different ways. To make it concise:
Baking Soda
-Single acting (does not require heat to start working)
i. Because it is single acting, it starts to react immediately. Thus, if you don't put your batter into the oven right away, all the gas (C02) created by the Baking Soda will escape
Baking Powder
-Avail Single or Double Acting (ie, reacts immediately, or requires both moisture and heat to fully react)
Baking Ammonia
-reacts very quickly, creating lightness, however, gasses may escape quickly if not baked immediately.
The reason why an excess of leaveners will collapse a cake, is because the gluten strands (Gluten = protein from flour that creats strands that gelatinize and become part of the product's structure) can only stretch so far and if you have too great a reaction at too short of a time, the strands will break and the cake will "collapse".
Now, as far as the eggs go, because of the protein content of the eggs, the emulsifying properties of the yolk, and the volumizing properties of the whites, if they are whipped/beaten and then folded into your batter, they are creating the structure for your cake (since there isnt much flour). If you think your cakes are collapsing because the eggs aren't stable enough, and if you are using egg whites, I would suggest adding a small amount of acid (cream of tartar, lemon juice,vinegar, etc) as that will help help stabilize and maintain the volume in the whites until they are baked/coagulated.
Another thing you could try is to decrease your butter just a tad bit. Although the fat helps with the overall mouthfeel and texture of the cake, it also shortens the gluten strands from your flour, and even though they are supported by the egg yolk, it could be that there is just too much fat for them to stabilize and 'set'.
'neway, I hope you're able to solve your collapsing problem, and if you do figure out what the cause is, please tell us ^^ Also, I hope everyones explanations will shed some light on the science behind baking...before I knew about coagulation/geltinization, and the roles of fats, eggs, leaveners, flours, etc in baking, I had no clue as to why things were happening! ^.^ hope you figure it out!
-moet