Method
1. Pre-heat oven - 175°C / 350°F
2. Grease a clean round pan
3. Add whole wheat flour, slivered almonds, rolled oats, brown sugar, salt and unsalted butter to a clean small bowl
4. Rub in until coarse crumbs form
5. Add unsalted butter to a clean small glass bowl, melt in microwave then set aside
6. Add egg, granulated sugar, salt and almond extract to a clean large mixing bowl
7. Whisk until triples in volume - approx 5 min, high speed
8. Add whole wheat flour and rhubarb whipped eggs
9. Add melted butter and fold until just combined
10. Pour batter into round pan
11. Sprinkle cake with crumbs evenly
12. Bake until golden brown - 1 hr 10 min, 175°C / 350°F
13. Transfer round pan onto cooling rack