You will need a spring form pan and parchment paper.
To toast the whole almonds, spread on a baking sheet and bake at 350°F (180°C) for 7 to 9 min until fragrant, stirring once or twice. To toast the sliced almonds, cook in a small frying pan over medium low heat, stirring constantly until lightly browned.
The eggs and lemons must be at room temperature for at least 30 min.
Preheat the oven to 350°F (180°C). Coat a 9 inch spring form pan with cooking spray. Line the bottom with parchment paper and spray it.
Grind the whole almonds in a food processor, blender or grinder until finely ground. It will make 13/4 – 2 cups (400-500 ml) packed. Grate the zest from the lemons and squeeze the lemons. You will get approximately ½ cup (125ml) of juice.
Separate the eggs and beat the yolks with the ½ cup (125 ml.) of honey, lemon juice, lemon zest, baking soda and salt in a large mixing bowl with an electric mixer until well combined. Add the ground almonds and beat on low until mixed.
In another bowl beat the egg whites with the electric mixer (with clean beaters) on medium speed until very foamy, white and doubled in volume but not stiff enough to hold peaks. Using a rubber spatula fold the egg whites into the almond mixture until just combined. Pour the batter into the spring pan.
Bake the cake until golden brown and a toothpick inserted into the centre comes out clean, 25 to 28 minutes. Let it cool in the pan for 10 minutes. Later run a knife around the edge of the pan and gently remove the side ring. Let it cool completely. Remove from the bottom with a large, wide spatula or flip it onto a serving plate.
If made ahead the cooled cake can be stored at room temperature in a sealed container for up to 1 day. When ready to serve drizzle the top of the cake with the honey, slightly warmed, and sprinkle with the toasted sliced almonds.