At first I couldn't think what you were referring to - an oatcake is a thin savoury biscuit (not an American style-biscuit, btw) that is eaten with cheese or breakfast!
I posted that I didn't know of anything similar to your sweet scone type cake... Then I remembered...... THE SELKIRK BANNOCK....
I think you are referring to a Selkirk Bannock - wonder if your Granny's friend was from the Borders? This is not to be confused with a normal bannock which is a kind of oat scone and eaten with savoury foods.
This originated in Selkirk and is still on sale at every baker's shop in the Borders area.... some are much better than others.
I wish I could give a source for this recipe, but I forgot to write down where I found it at the time, and my recipe is now a dog eared, handwritten copy, stained with fruit and fat stains!
NOTE There is no cinammon or other spice in this recipe, but I can certainly recall eating SB with a decidedly spicy taste - which I think may be cinammon.
300ml tepid milk
25g fresh yeast or 12g dried
½ tsp sugar
900g sifted flour
450g sultanas, slightly warmed
225g sugar, slightly warmed
125g candied orange peel (optional)
a little milk and sugar mixed for glazing
Heat the butter and lard until soft. Add the warmed milk and set aside. Cream the yeast with the ½ teaspoon of sugar, the milk and butter mixture and let the yeast go to work for about 10 minutes.
Sift the flour, make a well in the centre, and add the yeasted liquid. Sprinkle in the flour from the sides of the well to the centre so that it bubbles through and makes a batter. Cover with a cloth and leave in a warm place for about an hour or until it has doubled in size.
Knead well for 5 minutes then add the fruit with the remaining sugar and the peel. Knead for a further 5 minutes. Knead into a round flattish shape, cover and leave again in a warm place for about 45 minutes.
Bake in a medium oven 350F/180C/Gas 4 for about 1 hour. Take out the bannock and brush it with the milk and sugar mixture to glaze, then return it to the oven for a further 15 minutes. To test if it is cooked tap the bottom of the bannock ? it should sound hollow.