Combine thawed or fresh raspberries, sugar and lemon juice in a small sauce pan, and bring to a simmer overmedium to med/high heat.
Continue simmering and stirring while mashing the berries for about 12 minutes or until slightly thinner than desired consistancy. It will thicken a bit as it cools.
Strain through a fine sieve to remove seeds by stirring and pressing the mix into the sieve with a rubber spatula. If it’s not as thick as you want, you can put the sauce back into the pan to simmer and thicken if desired.
Place a spoonful on a plate and use the back of the spoon to drag across to make a swoosh or put it a squeeze bottle to draw more intricate shapes or words.