The wedding cake you are referring to is known as Chabela Mexican Wedding Cake. Here is the recipe:
175 g Refined granulated sugar
300 g Cake flour, sifted three
Grated peel of one lime
Place 5 egg yolks, 4 whole eggs, and the sugar in a large bowl. Beat until the mixture thickens and then add 2 more whole eggs; repeat, adding the remaining eggs two at a time until all the eggs have been added. When the last two eggs have been beaten in, beat in the grated lime peel. When the mixture has thickened, stop beating and add the sifted flour, mixing it in a little at a time with a wooden spoon until it has all been incorporated. Finally, grease a pan with butter, dust with flour, and pour the batter into it. Bake for 30 minutes. For the Filling: 150 grams apricot paste 150 grams granulated sugar To Prepare the Filling: Heat the apricot paste together with a little bit of water; after the mixture comes to a boil, strain it, preferably through a hair or flour sieve, but a coarser strainer can be used if you don't have either of those. Place the paste in a pan, add the sugar, and heat, stirring constantly, until the mixture forms a marmalade. Remove from the heat and allow to cool slightly before spreading it on the middle layer of the cake, which, of course, has previously been sliced into layers. For the Fondant Icing: 800 grams granulated sugar 60 drops of lime juice plus enough water to dissolve the sugar To Prepare the Fondant: Combine the sugar and water in a pan and heat, stirring constantly, until the mixture comes to a boil. Strain into another pan and return to heat; add the lime juice and cook till it reaches the soft-ball stage, wiping the edge of the pan with a damp cloth periodically to prevent the sugar from crystalizing. When the mixture reaches that stage, pour into a damp pan, sprinkle with water, and allow to cool slightly. After it cools, beat with a wooden spoon until creamy. To ice the cake, add a tablespoon of milk to the fondant, heat until it softens, add a drop of red food color, and frost only the top part of the cake with the fondant icing. Meringue icing: 10 egg whites 500 grams of sugar Beat together until they reach the coarse-thread stage. Frost rest of cake with meringue icing.
It looks like a pretty complicated recipe to me because you have to make the cake, the filling, and then the icing. The filling consists of two parts - an apricot paste and a fondant. Fondant is hard to get right. You can buy fondant in a baking supplies store, but it is not the kind of fondant that I think would work in this recipe because you cannot beat fondant that you buy in the store.
Also, this would make a HUGE cake - do you want it to be that large?
If you are daring, you could try this cake, but if you want to make something else that is authentically Mexican, you could try one of the other recipes from the movie - if you do an online search, you can find them. And, there is a Tres Leche cake that is much easier to make and is delicious, but not mentioned in the novel however.
If you make the Chabela cake, don't forget to cry into it, as in the novel, otherwise it will not be authentic!