Preheat oven to 350F (180C). Generously grease bottom and side of a 9-inch (23-cm) cake pan with oil. If using a springform pan, secure a sheet of parchment on the bottom of the pan when you're assembling it. Grease the parchment paper and place the cake pan on a baking sheet to catch any drips.

Slice rhubarb into 1/2-inch- (1-cm-) thick pieces. Place in a medium-size bowl.

Place jam in a small bowl and microwave on medium until melted, about 30 seconds. Pour jam over rhubarb and stir to evenly coat.

Evenly sprinkle 1/4 cup sugar over bottom of cake pan or pie plate. Spoon rhubarb mixture over top and evenly spread out. Dot with small pieces of the 2 Tbsp of butter.

In a medium-size bowl, stir flour with almond flour, baking powder, cinnamon, and salt.

In a large bowl, using an electric mixer, beat 2/3 cup butter until creamy, then beat in remaining 3/4 cup sugar until mixed, occasionally scraping down side of bowl. Add eggs, one at a time, beating well after each addition. Beat in almond and vanilla extracts.

Gradually beat in one-third of the flour mixture, then half of the milk. Repeat additions, ending with flour mixture, beating just until blended. Batter will be thick. Spoon evenly over rhubarb to completely cover, then smooth top as best you can.

Bake in centre of preheated oven until a cake tester inserted into centre of cake comes out clean, about 40 to 45 minutes. You may need to loosely cover the top with foil to prevent too much browning after 30 minutes or so.

When done, remove from oven and let stand 5 minutes. Then run a knife around edge of cake. Invert onto a large cake plate. Great warm or at room temperature. Cake will keep well, covered, at room temperature or stored in the refrigerator overnight. Serve with whipped cream.