Grease and line a 9 x 5 x 3-inch loaf pan / 23 x 13 x 6 cm with parchment / baking paper. Leave the paper to hang over the sides. This will make it easier to remove the loaf once it has baked.
Preheat the oven to 356°F / 180°C
Using a handheld beater or electric mixer, beat the butter and sugar until light and fluffy. Add eggs,one at a time, beating until just combined.
Add flour, baking powder coconut ( if using) and milk. Beat until well combined. Do not overbeat, just only until combined
Spoon ½ of the mixture into the lined pan. Spoon jam over top of batter, leaving a 2cm border. SEE NOTE 4
Top with the remaining batter and spread it over gently to cover. Bake for 30 to 35 minutes or until a skewer inserted into the cake comes out clean without any batter clinging to it.
Remove from the oven and leave in pan for 5 minutes. Transfer to a wire rack to cool completely.