Grab a small saucepan and put it on the stove over medium heat.

Add 1 cup of fresh raspberries and 1 and 1/2 tbsp of granulated sugar into the saucepan.

Flavor the mixture with 2 tbsp of lemon juice.

Cook the mixture until the raspberries break down. Mash some of the berries if needed and stir continuously to prevent sticking.

Lower the heat to a gentle simmer and continue cooking until the mixture thickens.

Once cooked, remove the raspberry puree from the heat.

Grab a heatproof bowl and place a fine mesh strainer over it.

Pour the raspberry puree through the strainer and discard any seeds or solids. Use a spatula to press down and extract as much juice as possible.

Once strained, you should have around 4 tbsp of raspberry sauce. If the amount is way more, return it to the stove and simmer until it reduces to the desired amount.

Cover and chill the raspberry sauce in the refrigerator for 2 hours.

Take a mixing bowl and add 1 cup of unsalted softened butter to it.

Use an electric beater to beat the butter for a few minutes on medium speed until it's smooth and creamy.

Gradually add 4 cups of powdered sugar, beating after each addition. Repeat until the sugar is fully dissolved.

Add the raspberry sauce to the butter and sugar mixture and beat until fully blended.

Continue adding the raspberry sauce to the frosting until you reach the desired raspberry flavor and consistency.

Taste to see if the flavor and sweetness are balanced. Adjust the raspberry puree or powdered sugar if necessary.

Get ready to spread the delicious raspberry frosting and decorate cakes, cupcakes, or your favorite treats as you wish!