Preheat oven to 325°F (160°C).
Generously butter 10 inch (25 cm) spring-form cake pan.
Place butter and lemon rind in large bowl; work butter until pliable.
Add sugar and cream together using spatula.
Add 1 egg and 3 tbsp (45 ml) flour and cinnamon; beat together with electric beater.
Add remaining eggs and beat until completely incorporated.
Place remaining flour with baking powder and salt in small bowl; mix together.
Sift half into egg batter and mix very well with spatula.
Pour in rum and incorporate with spatula.
Add remaining flour and continue incorporating.
Pour in milk and with spatula, mix until incorporated.
Fold in almonds.
Pour batter into prepared cake pan and rap bottom against counter to settle mixture.
Bake 40 minutes or until toothpick inserted comes out clean.
Remove pan from oven and cool 5-6 minutes.
Unmold onto wire rack and set aside until cold.