Line a 9 x 5 loaf pan with plastic wrap leaving a large overhang on short and long sides.
Combine egg yolks, sugar, vanilla, salt, blood orange juice and zest in a heatproof bowl set over a saucepan of gently simmering water. Make sure the bowl is not touching the simmering water.
Whisk continuously until the temperature reaches 160 degrees, about 5 min. Remove the bowl from the saucepan of water. Beat the mixture using an electric mixer until about doubled in volume and thick, about 5 min.
In a separate bowl or bowl of a stand mixer, beat the whipping cream until soft peaks form. Fold in whipped cream to the egg yolk mixture.
Transfer the mixture to the prepared loaf pan and smooth the top with a spatula. The pan will be very full. Fold the excess plastic wrap over top the semifreddo. Freeze for 8 hours or overnight.
Remove from the pan by carefully lifting up on the plastic wrap and invert onto a platter. Using a knife dipped in hot water, cut crosswise into thick slices. Top with the salted almond crumble.