Here is an English recipe for seedcake from Mrs. Beaton's. Recipe 2525, "A very good seed cake." Caution: Mrs Beaton was not a cook; all her recipes were from observation or taken down from a cook. Some adjustment in amounts of ingredients may be necessary. This edition of her book- 1888.

SEEDCAKE (Beaton)

1 pound butter
6 eggs
3/4 pound sifted sugar
Pounded mace and grated nutmeg to taste
1 pound flour\3/4 oz. caraway seeds
1 wineglass of brandy

Beat the butter to a cream; dredge in the flour; add the sugar, mace, nutmeg and caraway seeds, and mix these ingredients well together. Whisk the eggs, stir to them the brandy, and beat the cake again for ten minutes. Put it in a tin lined with buttered paper, and bake it from 1 1/2 to 2 hours. "This cake would be equally nice made with currants, and omitting the caraway seeds." "Average cost 2s.6d"

She also has a simpler one, a more likely cake for the Hobbit stratum:

Common Seed Cake (Beaton recipe 2524)

1/2 quartern of dough [2 lb.? see below]
1/4 pound of good dripping
6 oz. of moist sugar
1/2 oz. caraway seeds
1 egg

"If the dough is sent in from the baker's, put it in a basin covered with a cloth, and set it in a warm place to rise. Then, with a wooden spoon, beat the dripping to a liquid; add it, with the other ingredients, to the dough, and beat it until everything is very thoroughly mixed. Put it into a buttered tin, and bake the cake for rather more than 2 hours." "Average cost, 9d. Seasonable at any time."

Many definitions of a quartern in the OED; a quartern can be a 4 pound loaf made with a quartern of flour, thus she apparently means 2 pounds of flour.